I guess you can boot into "Recovery mode"
Please note that you are root there and you must be careful and never use startx
If you manage to boot into "Recovery mode" then do
Find the line that boots Mint normally. It looks something like
/boot/vmlinuz-2.6.22-14-generic root=/dev/sda7 ro quiet
Delete quiet and save the changed file - then reboot (normal boot)
Now you can see whats happening and where the boot stops. This tells a lot about the possible error.
You can do it from the live CD as well.