ok, My PC never had this problem before And Im sure its a Flash Player Update that started it.

But when watching videos on youtube, hulu etc. when at normal size I get horizontal Tearing in pans and high movement scenes. and full screen i get both tearing and choppiness, i used to be able to watch hulu shows fullscreen in 480p no problem. Now it can even watch them in the normal window.

I also see tearing when Im watching Saved FLV files, so it may very well be a codec Issue?

Its evident on my PC as well as my brothers, in FF, IE and Chrome. as well as stand alone .FLV players.

I had problems with Flash when I just DL'd the update and installed it...it wouldn't run any flash vids. I had to use their uninstaller which should be on their WWW site (uninstalling thru Win7 didn't work); and do a clean install. Not sure if it's the same problem, but you might give it a shot