3.3.1 boots fine, 3.3.1-1 only gets to the grub prompt. Wonder why?

Hi all! I saw the same topic mentioned before, and I know how to boot 3.3.1-1 using the Smart_BootManager boot cd, but just wandered if anyone knows what is the root cause of 3.3.1-1 only booting to the grub prompt?
Also, are there commands that I can issue at the grub prompt to force the 3.3.1-1 to boot on my system?
Many thanks.
serge.