I have been using ubuntu 12.04LTS for last few months, and now suddenly something has happened to it. As a result, terminal opens on every start up when I login . Although, if i login as a guest, it works fine. I have already used startx command, and tried reinstalling the desktop as well but it doesn't work! If I use ctrl+alt+f9, terminal screen vanishes and a black screen appears, and then nothing happens after that. ctrl+alt+f1 takes me to the command prompt. I know similar questions have been asked here, but i could not find a solution for my laptop. Please help!!