Problem with zune video and Radeon video card?

I just did a clean install of a ATI Radeon HD 5770 video card. Now I can't get video on my Zune software to play right. The frame rate is insanely slow, it's like watching a slide show. Video played in any other program runs just fine. Any ideas on a way to fix this?|||Yeah, don't use the Zune player...lol