A few more notes:
1) Safe boot didn't help
2) Repairing permissions didn't help
3) In iTunes --> Permissions --> Devices, there's nothing listed. None of my old backups show up (although they're apparently still in ~/Library/Application Support/MobileSync/Backup)
Because of #3, I'm a little leary of trying the hardware level reset on the iPhone
It turns out that I had to reinstall iTunes from scratch. I got the tip from
I'm 95% sure it had to do with me installing Xcode 4 to get the "FileMerge" utility for some other development effort totally unrelated to Xcode.
Regardless, it's working again.