Every page with div's which have overflow != hidden and are overfilled so a scrollbar appears are not displayed properly on Windows XP SP3. I checked this with 2 computers, the flexybrowser example and an own script. You can't use QWebView this way on XP for nearly every website.
Funny part: The elements are only displayed wrong, but seem to be 'physicaly' on the right positions, because you can select them where they should be.

3 screenshots below:
#1: Page loaded, everything alright
#2: Scrolled down a little bit. The bug is visible right now: everything moved around crazily, it looks like some of the items would be fixed, but they aren't
#3: Same scroll-Status as #2, but as already mentioned you can simply select the text where it should be