yes, indeed, it is a partition problem.
One question: Do you get the menu screen? (The Operating System screen: BT4, Memory Test, etc)?
You have 2 solutions:
1. If you get to the menu, you can use the grub console by typing "e" at menu...You will get a prompt: >, now you are in the grub console...Now start to repair the grub.
2. Use a live cd and mount partition (USB) and then fix grub.
Please, post if you get to the menu screen...As I said you have 2 options...
Hope it helps