Yup, I have BIOS 0901, which is latest. Also just found out that Windows users are reporting the same problem. Supposed fix is disabling Cool'n'Quiet in the BIOS. This worked, and after re-enableing CnQ it still works :-?
It could very well be that a fix for Ubuntu bug #118015  got snugged in when I ran the latest updates. The bug mentions a similar reboot problem which can be fixed by stopping 'powernowd' just before reboot, which means setting the cpu scaling governor back to no powersaving.
What part of the nvidia driver triggered this bug is stil a mystery to me.