When I got home from work it became immediately clear that things were not fine, as KDE was partially dead. I tried to vi /var/log/syslog and it said vi: command not found. Oh, this is bad. I couldn't even shutdown because it couldn't find that either. Switching to the console and trying to log in led to a string of I/O errors on /dev/hdc. Aha!
Next step was booting into a Knoppix CD I had lying around, which has saved my butt numerous times. It booted fine, of course, but then didn't find /dev/hdc at all. (/dev/hdc is my 320 GB I bought last year that has all my stuff except for music on it, so this is scary) I take a deep breath, shut it down, open up the case, clean out dust and check the connectors and such, reboot into Knoppix and presto, /dev/hdc is back! I rebooted into my real system and everything seemed fine after playing WoW, etc.
I went ahead and bought a new hard drive (after some persuasion from djedi) because if it's dying, it's dying (and there were definitely I/O errors on it before), so I have a new shiny 320GB SATA drive that I get to try to make my kernel work with. Hopefully I'll copy over data (takes foooorever) this weekend sometime.
I should add I'm a little irritated a hard drive I bought 15 months ago is dying already.