videos play media player but not media center

Hi,
I installed Vista Beta 2 and I can play MPEG2 and WMV files in Windows Media Player 11 but when I try to play the same files from within the Media Center I get the following error message:
"Files needed to display video are not installed or not working correctly". When I try to configure the Media Center for TV viewing I also get the same error message.
The same error message is displayed when I attempt to perform a TV setup procedure within Media Center. To support MPEG2 I installed the NVIDIA PureVideo Decoder Version 1.02-196 which appears to be the latest version. When I run the DECCHECK utility (the XP version - I couldn't find a Vista version) the NVIDIA decoder has a green checkmark for both MP and MCE compatibility and also is indicated as the preferred decoder. As far as WMV is concerned I'm just using whatever codecs come with Vista. I do have a non-Aqua compliant NVIDIA QUADRO 4 XGL 700 card but it seems that the hardware is not an issue since Vista Media Player 11 is quite happy playing MPEG2 and WMV files. Why is the Media Center complaining? The same PC multi-boots Windows XP and Windows MCE 2005 and both run MPEG2 and WMV files successfully from Media Player as well as from MCE.
Thanks, Anthony

-- zarbiker