inglishmayjer was one of several readers to send in the news of a major bug in Apple's new OS, 10.6 Snow Leopard, that can wipe out all user data
for the administrator account. It is said to be triggered — not every time — by logging in to the Guest account and then back in to the admin account. Some users are reporting that all settings have been reset and most data is gone. The article links to a number of Apple forum threads up to a month old bemoaning the problem. MacFixIt suggests disabling login on the Guest account
and, if you need that functionality, creating a non-administrative account named something like Visitor. (The Guest account is special in that its settings are wiped clean after logout.) CNet reports that Apple has acknowledged the bug
and is working on a fix.