Had this problem for a long time, the parts of web pages flash to white and then return back many times a second.
When I disable the adobe flash addon the web page is stable.
I have XP sp3,Ie8 and have just removed and reinstalled adobe flash player, I also had the same problem with Ie7.
Here is what I get I captured it when it was white in an area, I edited it so you can see where the content is missing.
I use have used firefox for a long time now with no problem in this area.