It would help us to help you if you posted more details. Did you have Ubuntu sucessfully installed and were you able to use it?
If so, what happened? changes made to the computer? other operating system(s) on it?
It is likely to be difficult to repair if you are unable to boot Ubuntu and don't have a Live/Installation CD or if you do not have the iso file to reburn. The error message you are getting happens when Grub is trying to directly boot a system on a filesystem it can't boot, usually windows. You can chainload windows but it won't boot directly from Grub.
Do you have any other Linux Live CD, GParted partition editor?? If not, you might download and burn GParted or a smaller Linux distro like Puppy Linux to get partition information to post.