Yesterday, I was setting up Linux on a new PC and went ahead with a custom partition table using druid. I didn't set up the /boot partition and as a result the grub configuration file (/etc/grub.conf) was incorrect. Then grub stopped at the grub prompt (thus giving me a chance to temporarily correct the problem)
I found this article very helpful in telling grub what I wanted, so that it proceeded with finding the Linux image and loading it.
Incidentally, this machine had a SATA drive, and ata_piix used to complain and kernel panic at boot, I removed the SSC pin (spread spectrum clocking feature) and it booted fine after that.