I wanted to post my own experience with this issue, as google returned this post in a search result...but there was never really a resolution.
Check the voltage of your BIOS battery. Mine was marked as a 3V battery, but only outputting 2V. It has never been replaced..so...these things happen.
I'm guessing the BIOS is write-protected if the voltage drops too low. You wouldn't want it trying to write data with low voltage and corrupt the flash memory.
It'd be really great if the BIOS warned you about that instead of just freezing.
I didn't have a battery to replace it with, but I cobbled up an adapter for a couple of AAAs (2 of them in series = 3V) and was able to save new settings after that.