I am new to ubuntu. I had been trying to install it and had been unsuccessful until i read something on one of the forums where someone had the same problem and logged in via gnome safemode.

My problem was that after installation, I would enter my username and password but ubuntu would return me to the login screen - in short, it was an endless login loop.

After getting in through gnome safemode, i went into the drivers area and saw that it had not installed a graphics/video driver because it was 'untrusted'. I gave ubuntu permission to install this and rebooted. It works now.

I beleive what was happening was after entering the password, it was trying to display something requiring the graphics/video driver, that failed, causing it to loop back to login.

I wanted to post this hoping that it would help the next person.