normally when you see " grub> " it means that the boot image can not be found
( you changed something fallowing this unnamed nsa guide )
normally reinstalling grub fixes it
boot into the install dvd and select "rescue mode"
then from that list reinstall grub
but WHAT nsa guide where you fallowing ?
did you by chance encrypt the boot partition or add a boot password to lock it from change ?
now seeing AS this is RHEL 5 you DO have a paid for red hat support contract
RHEL is not free
the full instructions for reinstalling grub are in the red hat knowledge base
search for " reinstall grub"
your RHN login username IS REQUIRED