I followed the steps described on
http://www.thefanclub.co.za/how-to/ubuntu-amd-catalyst-install
and now my ubuntu gives me the blank screen .. i tried a lot of things to uninstall ati catalyst but still unable too do so. So can any body please guide me how to do so
Edit:
I can connect to the internet in recovery mode.
My Graphic card is Amd Radeon hd 6490M