Hey,
I have experienced the same problem described by Robert. I have determined it only occurs when I view movies on machines where Flash Player 9 is installed. Dropping my machines back to Flash 8 seems to have sorted the problem out for my. Windows XP Pro with IE 7 Flash 8 works ok. Windows XP Pro IE 7 Flash 9 does not work well at all.
Hope that helps someone...
Regards,
Greg