I have had this problem before on an old Toshiba laptop... I think the problem you're having has something to do with the X11 setup. Try re-configuring the xorg server:
sudo dkpkg-reconfigure xserver-xorg
Hopefully this will fix your issue. If it doesn't, post some graphics card information with:
It's possible that you need to install a graphics card driver, this will help us help you in that instance.