Problem is that most of the time it says that the disk doesn't need repair and thus the error remains.
If you have the same problem, you can to the following to sort it out:
1. Restart your Mac.
2. As soon as it turns on, even before you hear it go bong, hold down Cmd+S.
3. The system will boot showing a lot of text. If it doesn't and you see the Apple logo, you've waited too long. Reboot and try again.
4. When at the prompt type fsck -f. If changes are successfully made it will repeat the process then say "Modifications have been made".
5. Then simply type in reboot and you should be able to partition your drive successfully.
