The first thing to do if you're experiencing unexpected behavior is to create a new account by clicking the + sign in the Accounts preference pane (in System Preferences). That way, if it doesn't occur in your new account you can be pretty certain that there's a problem with your current account. Now, if it happens to the other account, your next step would be to startup with the System CD and choose to "Archive and Install." Also, don't be stupid like me and purposely erase your drive when there's no reason not to, causing yourself undue grief.
