Problem with updated BIOS/ RMA mobo

Hello, received a replacement Biostar Geforce6100 M9 MB - working fine
except for this. It came with the newest bios,v.119 and when I put it all together, it crashed after an hour or so. Not a BSOD, but just a complete
freeze with an odd diagonal pattern on the screen. It occurred 2 or 3
other times, and not being able to find the problem (there were no dumps
or event log messages) I downgraded the board to the bios I had used on the
board I returned (for an unrelated problem) v.222. With this bios,
the new board is A-OK - no more crash.
How can I get to the bottom of this kind of problem - it might be useful
(but not imperative) to run the new BIOS because there's a few extra features in there that could be useful.
I have emailed Biostar regarding the crash but got not response.

Perhaps there's a bad default setting with the new bios - If I could track it
down it would be great.
Any thoughts?
Thanks, Dave