I have a Macbook Pro set up with a dual boot into OSX and Ubuntu 9.04. The system is wonderful, and for five years I have never had even a hint of a problem. It is set up with rEFIt, so when you boot up it first goes to the rEFIt menu screen where you select OSX or Linux. If you select Linux (which I do 99% of the time), it then goes to the standard GRUB menu screen, where upon selecting Ubuntu (the only OS set up there), it boots up into Ubuntu. This morning out of the blue when I boot up and select Linux at the rEFIt screen, it acts as though a GRUB menu screen is about to appear. But instead of that, it just gives a black screen with the words "GRUB" appearing in the upper left hand corner of the screen. So I am guessing that perhaps GRUB became corrupted somehow. What do I have to do to get GRUB working again? (This is urgent-- I can't do any of my work until GRUB works, so I can get into Ubuntu.) Thank you!