From the Grub 2 menu, press "c" and see if you can boot from the command line. The good thing about this method is that you will be able to tell if Grub can find the correct files by using TAB to complete the entries. For now we will assume sda1 is the correct location of the linux system. The # and what follows are not entered, just explanations, except in the linux line, where you have to add "root=/dev/sda1 ro" after the kernel is entered.
Originally Posted by sejsen
These steps are outlined in the GRUB 2 community doc:
ls # Press ENTER and you should see (hd0), (hd0,1) at least.
linux /boot/vml # then tab. It should add all or most of your kernel, you may have to add the specific kernel number; then add root=/dev/sda1 ro
initrd /boot/initr #then tab to complete the initrd image
Using CLI to Boot
If you can boot you will then have to figure out what is wrong with the main menu. The first thing to do would be to run:
sudo grub-install /dev/sda