My Ubuntu OS won't boot; Why?

Hi -- Your forums were quite a help to me when I was building this computer, so thank you again for that!

My dual Hard Drive system (AMD Quadcore, 64-bit, 4 Gb RAM) has been running fine for quite awhile. I've got Windows XP on the older smaller HDD, & it still boots up fine. I have Ubuntu 11.10 on the newer 320 Gb HDD, by itself, SATA-connected, with plenty of Swap. I've had trouble booting this OS back up after trying to suspend or hibernate (it won't). But this time, my Ubuntu OS won't boot after a perfectly normal shutdown. No graphic, no sound, no HDD light activity.

In the past, I've had to wipe this Hard Drive, reinstall, then reinstall all programs, pref's, etc. Quite time-consuming. I'm beginning to suspect this may be a hardware problem, rather than software. How can I discover if the 320 Gb HDD is bad? If it were bad, could it work sometimes & not other times? I can access my Ubuntu installation by using an Ubuntu Live CD. Is there some way to recreate it or repair it without wiping the drive? Disk Utility says the drive is fine. What tests can I do to pin this problem down?

Thanks!!