[ubuntu] Screen stalls upon install 12.04

I just made a fresh install of 12.04 on a machine that used to tun 10.04.

I installed from a USB, the machine asked for reboot in order to finish the install. I did, logged in and my screen went strange. Now I cannot even get to the login screen. Guess this is a video card issue but have no idea how to solve this.

Tx