Oddly enough I have exactly the same issue with the MSI 650 1GB. As soon as the nVidia driver is loaded, the fan gets stuck at 100% and cannot be changed.
I do not get this issue with the Nouveau driver so it is specific to the nVidia official driver blob.
Driver is the latest, 313.30-5. I've also tried the 319 beta.
Enabling coolbits gives me fan control in the nVidia settings program, but I can't change it - if I try then as soon as I hit Apply, the slider jumps back to 40% and nothing happens.
I've put the bug report log on the new forum - https://devtalk.nvidia.com/default/t...ocked-at-100-/