one good solution is to get either a live-cd or some other linux cd you can boot from...I suggest live-cd since it enables you to do a lot of fixing stuff
like Knoppix does.
you can simply edit the root= -line in your grub config, if that's the problem. I'm not sure what the problem really is so I don't know if I can help, but check out that the root= -line in your config includes the correct path(s)...like /dev/hda1 for hd partition 1 and so on, and nothing wrong.
if you have DSL and an empty cd, download Knoppix and burn it...and you're done.