To experience the first (Windows) issue,just play a HD WMV wideo (not VC-1) in Windows Media Player on a fresh install of XPSP3.
Here's a quick way to reproduce the video playback issue on Windows: Download the MotoGP '08 demo available at nVidia's nZone page:
http://www.nzone.com/object/nzone_motogp08.html
Just install the game demo,go to the Movies folder and try to play any of those HD WMV videos with Windows Media Player or Media Player Classic)
For the Linux issue,I'll have to try Catalyst 9.1 again (this time with some kernel tweaks) and see if there are any improvements. Stay tuned.