Using Mandriva Linux 2010.0, when my desktop system tries to restart from hibernation, it locks up (power still on) at the point where control gets passed from BIOS to MBR or live CD/DVD. If power is cycled, it invokes SBM and from there it goes to a successful recovery from hibernation. This prevents unattended operation, as I have my UPS configured to have the system hibernate at a power outage, and restart when power returns.
I reluctantly replaced SBM with GRUB, and the system correctly restarted from hibernation as soon as it was powered up. That's why I suspect the problem is SBM. Send questions, comments, requests for more info to me at "adam seven zero seven AT verizon DOT net". Thanks for all your work on this project!