I am running ubuntu 12.04 and yesterday i installed a few updates. i cant recall which. Afterwards i shut down the pc.
Today when booting up, i can see strange artifact behaviour in the login screen. a few black blocks appeared. and as i type my password i can see some white jibber appearing in the black blocks.
when providing my password and logging in, the computer freezes (black screen), monitors go into sleep mode and all i can do is force off the pc.
However i am able to log in succesfully as guest !! How can i troubleshoot my pc, i noticed i can not sudo from the quest account.