The Tech Report writes Mac OS X users have discovered a nasty bug in Snow Leopard. The report says logging into the "Guest" account then back into a regular user account can wipe one's profile and the data stored in user profiles, including documents and music.
The site points to two threads on the Apple forums where different users complain of the problem: one thread dated September 3 and another from September 12. The users claim the Snow Leopard bug doesn't just reset their preferences, it also wipes data stored in their user profiles, including documents and music.
iTWire says the issue may only crop up when someone upgrades from an OS X 10.5 Leopard installation where the "Guest" account was already enabled. One way to prevent the problem might be to disable the account then re-enable it "so that it's a native Snow Leopard account." Or, you know, just disable the Guest account and stay well away for now.