While booting (BIOS went fine), I just got:
Errors were found while checking the disk drive for /
Press F to attempt to fix errors, I to ignore, S to skip mounting or M for manual recovery.
After pressing F, it checked my drive and rebooted the system, again presenting the dialog above. Then I pressed I, it continued correctly and I backuped my files.
It might still be a CMOS battery problem.
The fix could range from anything from checking the disk http://ubuntuforums.org/showthread.php?t=1535761
to replacing the drive http://ubuntuforums.org/showthread.php?t=1684746