When I select Ubuntu from the GRUB screen I get this error message:

"Error: Attempt to read or write outside of disk 'hd0'

Press any key to continue..."

I've been getting this error for a few days and I click any key and it boots normally, but today it just became unresponsive when I pressed any key and doesn't boot into Ubuntu.
Any way to fix this?

I'm using ubuntu 12.10 and running it alongside Windows 7 by the way.