Keyboard layout \"gone mad\" - can\'t log in after sleep



this time I'm stumped myself: I just woke up my Mac mini (by pressing a key on the keyboard), then connected to it via VNC from my other Mac and, since I enabled the "Require Keyboard to wake up etc." option, the first thing that I saw was the login window (as usual).

However I can't enter my login and password since, both remote via VNC and using the attached keyboard, nearly all keys I press generate greek letters and other symbols - not even the return key works; it clears the input field.

Does anybody know a short-term fix so that I can log in?
Does anybody have an idea of where the problem came from in the first place?

Computer is a Mac mini with Mac OS 10.4.3 Server and the built-in Remote Desktop Server.

Thanks, Colin