So I booted up my mid-2011 iMac this morning (running 10.6.8) and it automatically went into Safe Mode. Not only that, I noticed in my dock that an app had been 'question marked'. I restarted with no issues but the application has definitely disappeared altogether from my Applications folder.
Right now, I can't really tell if any other applications have gone as I've got so many and this one was the only one in the Dock. It's certainly a puzzling affair though.
Strangely enough, I did that only days ago when trying to sort out my drive to do a Boot Camp partition. I guess it can't hurt to try it again. Seems like only one application went missing so far anyway.
EDIT: Additionally, the drive still wouldn't partition. Bummer.