Vista - User Login Screen

Hello-

I am using Vista Home Premium. At the User Login Screen, where I have 3
accounts set up, when I selevt my admin account (or any account for that
matter) the login fails. Windows fails to ask for a password, the mouse shows
the "loading" animation "donut" and acts if it is going to load. Then, the
screen turns blank, showing the background of the Vista login screen only,
then all of the sudden bounces back to the main login screen where all the
user accounts are shown. Basically, when I select any user to login, it just
bounces back to the login page. I've attempeted to repair windows and use
system restore to no avail. The same thing happens under safe mode as well.
Anybody have any suggestions?

Thanks

-Patrick