The hibernation situation is not the main issue. It was something I encountered while trying to reproduce the original problem. Its cause and solution are exactly as you describe.
I'm thinking it is probably a completely unrelated problem, but there might be a connection between hibernation and the data in the last sector.
The main problem, as experienced by others herehttp://s10lenovo.com/viewtopic.php?f=10&t=2745
is when the computer will not boot under any circumstances as long as the hard drive is installed.
This seems to be due to the bios expecting either valid data (about what I don't know) or zeroes in the last sector of the hard drive.
Pulling the hard drive, zeroing the last sector, and reinstalling the hard drive seems to fix the problem, with no loss of data.
Leaving some unallocated space at the end of the drive seems to have prevented a re-occurrence.
I'm surprised the problem took so long to appear.
My best guess is that even though I first repartitioned my hard drive a year ago, I didn't actually write anything to the last sector until my most recent repartitioning -- or at least I didn't write anything that the bios would try unsuccessfully to interpret, cause it to hang at boot time.