I am really glad this thread has appeared, so glad I joined the site :)
I have tried everything ( short of the rollback option ) with no luck. Having gone over
the KB950126 release information theres a little sentence that reads :
" This update addresses a blank screen issue that occurs when you switch between full-screen mode and windowed mode while you play videos. "
All I can say is ... Hmmmmmmm
The issue manifests itself when VMC loses focus , either when resizing , screen saver kicks in, minimzing, maximising or running some web based content, in my case TunerFree MCE ( formally Iplayer MCE )
Its completely predictable and more than a little annoying. Its favourite party piece is , screen goes blank for screensaver etc , movie resumes or restarts.