I had a similar issue, except I was getting constant VPU recovery errors with my "new" ATI card.
After I did swap out the P/S for a new one, I figured it was probably overheating. (gogo crappy driver support as well...)
Thankfully it was a desktop and not a laptop tho.
I don't see how switching to 16-bit mode instead of 32-bit mode would have any impact, but I guess, it's worth a shot.