OK, I've found another error code.
When the backup stalled (with no error codes in the rather useless widget) and the finder locked up, I force quit the finder using Activity Monitor to try to get the Finder to re-launch -- though I knew it wouldn't. However, upon clicking the finder icon in the dock, I got an error -10810 telling me that the finder couldn't be launched.
Here's everything from the system.log in the console from that backup attempt forward.
ct 15 09:37:24 Bryan-McCoys-new-Computer com.apple.backupd[476]: Starting standard backup
Oct 15 09:37:24 Bryan-McCoys-new-Computer com.apple.backupd[476]: Backing up to: /Volumes/300GBBackup/Backups.backupdb
Oct 15 09:37:32 Bryan-McCoys-new-Computer com.apple.backupd[476]: Event store UUIDs don't match for volume: Macintosh HD
Oct 15 09:37:32 Bryan-McCoys-new-Computer com.apple.backupd[476]: Node requires deep traversal:/ reason:must scan subdirs|new event db|
Oct 15 09:37:52 Bryan-McCoys-new-Computer iChatAgent[489]: [Warning] [AIM] Failed to load own icon from cache, can't upload to server.
Oct 15 09:38:00 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:5.044104, # of Inserts: 2, # of bytes written: 821209, Did shrink: NO
Oct 15 09:38:04 Bryan-McCoys-new-Computer com.apple.WebKit.PluginAgent[498]: Debugger() was called!
Oct 15 09:39:19 Bryan-McCoys-new-Computer com.apple.backupd[476]: No pre-backup thinning needed: 2.31 GB requested (including padding), 88.76 GB available
Oct 15 09:40:18 Bryan-McCoys-new-Computer DashboardClient[527]: com.bluedog.tmwidget.TimeMachine: ERROR: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2
Oct 15 09:40:18 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:18.891 DashboardClient[527:a03] com.bluedog.tmwidget.TimeMachine: ERROR: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2
Oct 15 09:40:18 Bryan-McCoys-new-Computer DashboardClient[527]: (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2 (line: 33)
Oct 15 09:40:18 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:18.892 DashboardClient[527:a03] (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2 (line: 33)
Oct 15 09:40:18 Bryan-McCoys-new-Computer com.apple.backupd[476]: Copied 2990 files (1.0 GB) from volume Macintosh HD.
Oct 15 09:40:19 Bryan-McCoys-new-Computer com.apple.backupd[476]: No pre-backup thinning needed: 1.05 GB requested (including padding), 87.73 GB available
Oct 15 09:40:20 Bryan-McCoys-new-Computer DashboardClient[527]: com.bluedog.tmwidget.TimeMachine: ERROR: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed
Oct 15 09:40:20 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:20.646 DashboardClient[527:a03] com.bluedog.tmwidget.TimeMachine: ERROR: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed
Oct 15 09:40:20 Bryan-McCoys-new-Computer DashboardClient[527]: (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed (line: 33)
Oct 15 09:40:20 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:20.647 DashboardClient[527:a03] (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed (line: 33)
Oct 15 09:40:22 Bryan-McCoys-new-Computer com.apple.backupd[476]: Copied 1368 files (2.0 MB) from volume Macintosh HD.
Oct 15 09:40:25 Bryan-McCoys-new-Computer com.apple.backupd[476]: Starting post-backup thinning
Oct 15 09:40:26 Bryan-McCoys-new-Computer DashboardClient[527]: com.bluedog.tmwidget.TimeMachine: ERROR: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed
Oct 15 09:40:26 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:26.963 DashboardClient[527:a03] com.bluedog.tmwidget.TimeMachine: ERROR: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed
Oct 15 09:40:26 Bryan-McCoys-new-Computer DashboardClient[527]: (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed (line: 33)
Oct 15 09:40:26 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:26.964 DashboardClient[527:a03] (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed: Unrecognized message format: Oct 15 08:58:32 Bryan-McCoys-new-Computer com.apple.launchd[1] (com.apple.backupd[8445]): Exited: Killed (line: 33)
Oct 15 09:40:29 Bryan-McCoys-new-Computer com.apple.backupd[476]: Deleted backup /Volumes/300GBBackup/Backups.backupdb/Bryan McCoy’s new Computer /2009-10-14-083755: 87.77 GB now available
Oct 15 09:40:30 Bryan-McCoys-new-Computer DashboardClient[527]: com.bluedog.tmwidget.TimeMachine: ERROR: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2
Oct 15 09:40:30 Bryan-McCoys-new-Computer DashboardClient[527]: (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2 (line: 33)
Oct 15 09:40:30 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:30.643 DashboardClient[527:a03] com.bluedog.tmwidget.TimeMachine: ERROR: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2
Oct 15 09:40:30 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:30.643 DashboardClient[527:a03] (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed\]'' return code: 2 (line: 33)
Oct 15 09:40:33 Bryan-McCoys-new-Computer com.apple.backupd[476]: Deleted backup /Volumes/300GBBackup/Backups.backupdb/Bryan McCoy’s new Computer /2009-10-14-073716: 87.77 GB now available
Oct 15 09:40:33 Bryan-McCoys-new-Computer com.apple.backupd[476]: Post-back up thinning complete: 2 expired backups removed
Oct 15 09:40:33 Bryan-McCoys-new-Computer com.apple.backupd[476]: Backup completed successfully.
Oct 15 09:40:44 Bryan-McCoys-new-Computer DashboardClient[527]: com.bluedog.tmwidget.TimeMachine: ERROR: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed (line: 33)\]'' return code: 2
Oct 15 09:40:44 Bryan-McCoys-new-Computer DashboardClient[527]: (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed (line: 33)\]'' return code: 2: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed (line: 33)\]'' return code: 2 (line: 33)
Oct 15 09:40:44 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:44.226 DashboardClient[527:a03] com.bluedog.tmwidget.TimeMachine: ERROR: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed (line: 33)\]'' return code: 2
Oct 15 09:40:44 Bryan-McCoys-new-Computer com.apple.Dock.agent[161]: 2009-10-15 09:40:44.227 DashboardClient[527:a03] (com.bluedog.tmwidget.TimeMachine)
file:///Users/bryanmccoy/Library/Widgets/Time%20Machine%20Buddy.wdgt/Utilities.j s: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed (line: 33)\]'' return code: 2: Unable able to execute command line: 'bzcat /var/log/system.log.0.bz2 | cat - /var/log/system.log | grep -E 'backupd\[8445]): Exited: Killed (line: 33)\]'' return code: 2 (line: 33)
Oct 15 09:41:27 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:6.886549, # of Inserts: 193, # of bytes written: 2645427, Did shrink: NO
Oct 15 09:41:36 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:6.115388, # of Inserts: 27, # of bytes written: 3424349, Did shrink: NO
Oct 15 09:44:45 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:10.163149, # of Inserts: 1, # of bytes written: 25, Did shrink: YES
Oct 15 09:44:52 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:6.959761, # of Inserts: 0, # of bytes written: 0, Did shrink: YES
Oct 15 09:45:00 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:7.750157, # of Inserts: 0, # of bytes written: 0, Did shrink: YES
Oct 15 09:48:19 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:3.806519, # of Inserts: 2, # of bytes written: 8069056, Did shrink: NO
Oct 15 09:48:26 Bryan-McCoys-new-Computer Safari[483]: INSERT-HANG-DETECTED: Tx time:5.597533, # of Inserts: 0, # of bytes written: 0, Did shrink: YES