Update:
I went for a few days with no crashes until yesterday. Before I went to bed last night I quit all open applications including Activity Monitor, set the Energy Saver to never sleep either the CPU or the display and manually put the display to sleep with a hot corner. When I got up this morning it was locked up: I hit space bar to wake the display (shows PW box and the clock in the control bar, however the clock shows a time not associated with a crash, approximately 3 hrs prior to when the display was last put to sleep), entered password and got the beachball. Had to do a hard reset.
Here are the last four lines from the log and the start of the reboot copied from Console:
6/28/12 1:24:27.850 AM com.apple.backupd: Backup completed successfully.
6/28/12 2:19:05.516 AM com.apple.backupd: Starting standard backup
6/28/12 2:19:05.687 AM com.apple.backupd: Backing up to: /Volumes/Time Machine/Backups.backupdb
6/28/12 2:19:06.139 AM com.apple.backupd: 2.77 GB required (including padding), 358.28 GB available
6/28/12 5:49:54.000 AM bootlog: BOOT_TIME 1340887794 0
Configuration: New Mid 2012 13" MBA w/ 1.8GHz i5, 8GB, 256GB SSHD