Sounds like the Grub configuration file got blown out or the drives got re ordered in the bios. Grub reads from the bios first connections starting at number 0. So hd0 is the first drive connected.
Since it is confused you need to tell it what to do. You need to define the root device, kernel, initrd filename then tell it to boot.
root device -- at the prompt : root (hd0,0)
-- this would be physical drive 1 partition 1
kernel -- Next Prompt : kernel /vmliuz-2.6.38.dmz.1-liquorix-amd64 ro root=/dev/hda1
-- this is mine, not sure if at this prompt you have auto-completion if you are unsure of the naming convention. After typing your best guess hit the tab key and see if it gives you a hint.
initrid filename -- third prompt : initrd /initrd.img-2.6.38-4.dmz.1-liquorix-amd64
-- again try using auto-completion to get the correct naming convention.
boot -- last prompt : boot
-- just type boot & hit enter.
-----If you get stuck with this option you could also use a live cd to boot and reinstall grub.-----
If all works out you should boot at which time you should reinstall grub.
Here is a link on the grub manual which should help. You can also go to a command prompt & type info grub for an offline manual.
I am no expert (actually a bit of a newbie) so if a another member sees a better way to approach please offer some input.
Hope this helps