I recently ran into an issue whre I connected to an XP machine with remote desktop and the background would not repaint when windows were closed or moved.  I found that the Windows Security Center and the system tray notification about the Antivirus not working were running (wscpui.cpl and wscntfy.exe) under another user's account.  When I stopped those processes, then the background would repaint again.  So, if you see this behavior, you might check for processes running under another user's session.