Critical error in Mac OS X 10.6 leads to data loss
It would seem: Snow Leopard is finished and released. But it was not there. A lot of reports fell in the network that even a random entry into the Guest account can erase the data on the main account to hell. "Sorry sir, your car cannot be restored." It all goes something like this: someone upgraded to 10.6, enters the guest account and the car almost hangs. There is a huge chance that now after you enter the main registration there will be a burnt desert.
Apple stated that it already knows about this error, which occurs in extremely rare cases, and that they are already working on a fix. In the meantime, the point is, good advice would be to disable the guest account.