Have just upgraded mine to "Latest nVidia 195.xx (STABLE) 195.36.15" and found these methods worked well
Ubuntu NvidiaManual (https://help.ubuntu.com/community/NvidiaManual)
Ubuntu forum post (http://ubuntuforums.org/showthread.php?t=990978)
Nvidia Unix Drivers Portal (http://www.nvidia.com/object/unix.html)
HOWTO: Automatically update manually installed NVidia drivers after kernel updates (http://ubuntuforums.org/showthread.php?t=835573)
I had no problem upgrading to the 195 drivers but I still haven't managed to get Collatz to run on Ubuntu. :(
I received this email from Nvidia UK where I am listed for news updates - I think it only refers to the Windows Drivers though:
"196.75 GeForce Alert!
We are aware that some customers have reported fan speed issues with the latest 196.75 WHQL drivers on NVIDIA.co.uk. Until we can verify the root cause for this issue, we recommend that customers stay with, or return to 196.21 WHQL drivers. The 196.75 drivers have been temporarily removed from our website."