Oh man !!
You have this SIS graphics card..
Sorry ... I cannot help you with that.
The only thing I can suggest is to try to upgrade the driver through a PPA.. (maybe)
You can see the current installed driver with this command
apt-cache policy xserver-xorg-video-sis
The Xorg-edgers PPA have a newer version .. (almost always) in their repository.
apt-cache policy xserver-xorg-video-siliconmotion
If you want to update and test run
Be aware that this repository is NOT considered as stable , read the description.
sudo add-apt-repository ppa:xorg-edgers/ppa
sudo apt-get update
sudo apt-get dist-upgrade
Also you can try to add the sis module to /etc/modules and see if this can help ..
In case of a problem with the upgrade of driver you can revert back with
echo "sis" | sudo tee -a /etc/modules
Thats all my suggestions about this chip.
sudo apt-get install ppa-purge
sudo ppa-purge ppa:xorg-edgers/ppa
sudo apt-get update ; sudo apt-get dist-upgrade