After locking Vista some letters on my keyboard act as hotkeys. U (which is in my password) brings up the “Ease of Access” window. Needless to say, this makes the login process impossible to complete.
This only happens if I run Virtual PC (2007) when locking Vista. So I guess VPC is to blame, but I’m sure there are other programs out there that might cause this behaviour too…
Quite simple really. Click the “Switch user” button and select your own account. Hotkeys are gone!