Re: 260GTX nvidia-drivers-190.42-r3 - powermizer issue
I recently investigated two configurations that exhibited behavior consistent with that described in this thread. One was using a GeForce GT 240, the other a GeForce GTX 260M.
The former turned out to be a memory training problem affecting all GT21x GPUs with SDDR3/GDDR5 memory; it should be fixed in future NVIDIA Linux graphics driver releases.
The latter is ACPI related and, while understood, not yet resolved. Unfortunately, I can't estimate/speculate when a fixed driver may become available.