This bug is not specific to his motherboard. Here is a thread I started on the same bug: http://www.nvnews.net/vbulletin/showthread.php?t=186171
I set Coolbits to 4, but when I change the fan speed setting, the speed doesn't change at all. And it's not running at 100%, even though nvidia-xsettings says it's at 100%. My system is overheating regularly, causing the BIOS to reduce the CPU frequency from 2.2 GHz to 800 MHz.
None of this happened until I upgraded to Ubuntu 12.04. I've been running Ubuntu on this laptop since 8.04.
Dell XPS M1330
NVIDIA GeForce 8400M GS
driver version 295.20+
I guess I'm going to have to further downgrade the driver. I hope it works, but eventually I guess I'll run into it not working with newer versions of X or the kernel. It's already giving me trouble with DKMS.
NVIDIA, please fix this. This is a completely new regression in the drivers--it's worked fine for YEARS until now. Someone broke something in the drivers, and it's causing real problems with hardware. It's probably shortening my laptop's life (this is one that had a BIOS update come out to force higher fan speeds due to the faulty 8400 chipset packaging, but now the fan isn't running at full speed).
If you can't reproduce it, do this: get a laptop with an 8400M GS, install Ubuntu 12.04, install 295.20 or later, and boom, problem.