[Lucas]

I would try creating a new user account on the same machine and see if the same thing happens. If it does, you might try a system reinstall, which might work, but I would guess that it is a hardware problem at that point. If it doesn’t, then you might try moving all the contents of the Library/Preferences and Library/Application Support into folders on the desktop (and trash the contents of Library/Caches) and see if that fixes it. This kind of sounds like a FileVault problem - you don’t have that running on your system do you? Another prime suspect would be dropbox - are you using that to sync?