actually, it sounds like an all too familiar problem. just download the latest 5.2 catalyst drivers from ATI.
here's the link for both english and international drivers:
http://www.ati.com/support/driver.html)
just select your operating system in the first column, then the "Graphic Driver" option in the middle column, and then the select the "RADEON family" option in the final column. then hit the go button.
the new drivers should solve your problem. :)