When I researched your question, I came up with some odd answers. Have you rebooted? That has solved the problem for others. Also it is usually caused by some stuck keys. Is this a laptop we are talking about? Tap on your CTRL key, you ALT key and your DEL key a few times each (separately lol). It looks like this isn't a Vista problem but a strange hardware one. Let me know if any of this works for you please, I'm going to look a little more to see what else I can find........
EDIT: I found some more stuff here
Edited by DeathStalker, 19 March 2010 - 07:57 AM.