Comment 3 for bug 386028

Maybe you have resized the root partition and so the uuid has changed, than system can't boot because it can't find the partition with old uuid. More info on the following link.
http://www.linuxmint.com/wiki/index.php/UUID_-what_is_it_and_why_is_it_a_problem

Start with live cd, then run the command

ls -l /dev/disk/by-uuid/

Then edit the file fstab and change the uuid of the / mount to the right one.