Have you installed the newest Catalyst drivers, made sure the card was properly seated, yadda yadda yadda?
Building a computer is a rewarding experience, and teaches you the fundamentals of life.....which is, life sucks sometimes, doesn't it?!
Seriously though, I would download and install the newest Catalyst drivers from ATI and see if that takes care of your problems. From what you describe, it sounds like something in the driver install either got corrupted, or is acting goofy for some reason.
Uninstall the drivers, set the vid adapter for Standard VGA, and reboot, Install the new drivers, take 2 and call us in the morning