Comment 32 for bug 1316035

Find a way to workaround.

I have a PowerEdge R620 which installed a Ubuntu 12.04 TLS. And I found the screen refreshing became very slow. So I share the same issue with yours.

First,then we have to install vesa driver:
sudo apt-get install xserver-xorg-video-vesa

Then, for some of the Ubuntu release don't have a xorg.conf, so I have to generate one with following steps:

1.switch to console mode: Alt+Ctrl+F1
2.kill x server: sudo service lightdm stop
3.generate new xorg.conf file: sudo X -configure -- this will create xorg.conf.new file in your current dir
4.rename and move: sudo mv xorg.conf.new /etc/X11/xorg.conf
5.open /etc/X11/xorg.conf, replace the graphic driver of 'mga' with 'vesa'.t
6.return to GUI: sudo start lightdm