I have been experiencing an issue since I've up upgraded to Windows 7 where all flash videos have horrible frame rates when run in full screen mode. I have tried multiple browsers and i have the latest version of flash and video drivers. I have tried re-installing flash and disabling hardware acceleration. The problem occurs on youtube and hulu.
This is a clean install on a Core 2 duo with 4GB RAM and an Nvidia 8400M GS.