One of these days, I may finally learn not to tinker with things when tired.
I had the SD card from my Cubiboard mounted on my desktop, and was changing some files to allow it to boot again.
Silly me didn't make note of what directory I was in, and ended up removing a vital folder on my desktop PC (/var). Thankfully, I noticed my error before I powered down for the night, so I was able to back up a couple system config files that will make reinstall easier.
I wont be losing anything other than time, so I'm more amused than upset. It has been literally years since the last time I really broke my computer.