[drenkrom]

Did you try deactivating the root user in your Directory Utility? I may be mixed up in my Mac OS versions, but I think it's in the Edit menu of the Directory Utility found in the Utilities folder inside Applications. Reactivating it when you need it takes a few seconds, so I always deactivate it after use (or just use sudo in Terminal).

If your root user is deactivated and you still get that message, you're really in weird territory. It may be worth opening Terminal and entering the "sudo password root" command, where "password" is your root user password, which should switch the root user's state.