recently, i submitted a bug against wine, which they believe to be an issue with xfce itself. i don't really believe them, but i figured i would go ahead and run it by you anyway.
certain games under wine end up with part of their screen unrendered undered xfce. the same games work just fine under gnome. note that a lot of games work fine under both xfce and gnome; hence the reason that i think the problem is within wine itself.
you can see the original wine report . thank you for any thoughts you have on the matter.
Not sure I understand the original description, but could that be either xfce bug #3482 or #5030
As a start, I would suggest trying xfce 4.6.1 that contains a fix for the two bugs mentioned above (both affecting wine in fullscreen).
This issue is (still?) present in XFWM 4.8.3. Apparently it also happens with IceWM, but not with other window managers such as Metacity.
WINE report: http://bugs.winehq.org/show_bug.cgi?id=30213
IceWM report: http://sourceforge.net/tracker/?func=detail&aid=3514302&group_id=31&atid=100031
Apparently "the window manager
resizes the fullscreen (after the mode change) window to the (original)
desktop size instead of keeping it at the current screen size".
Duplicate of bug #8622 then.