Mac OS X Snow Leopard Bug Eats Files Page: 1
Apple OS X Bug
A pretty major bug in the latest edition of the Mac OS X operating system - Snow Leopard has seen users lose the majority of their personal data and settings. The bug isn't hard to trigger either, all it requires is the user to log on to the built in Guest acount, just once, and then bam, all of their data is gone. You'll log back in to find your data from /Users/username gone, permanently.
Users are reporting that restoration utilities and professional data recovery experts can not retrieve the data, the only way is with a backup. This has existed for some time, but only now, when it was affected many people, has Apple responded to it, saying they "are aware of the issue, which only occurs in extremely rare cases, and we are working on a fix". Apparently, you're less likely to suffer the loss if you have upgraded from Leopard to Snow Leopard, if you bought your Mac with Snow Leopard already installed, you're far less likely to suffer any loss.
It's ironic that the Guest account, designed to protect your personal data makes you lose it all. It seems all you can do for now is disable your Guest account and make sure you have a backup of your important data.