Laptop freezes after installing CUDA 6.5

Hi all,
I am trying to install CUDA 6.5 onto my Ubuntu 14.04 laptop with Nvidia Geforce GT 720M. The installation was going smoothly, I can run the CUDA examples. However, my computer usually freezes after 5 to 10 minutes. I tried to reinstall the driver, switching between 331.38 and 340.29, but it does not work.
Do you know any solution for this issue. Thanks.

331.38 is not compatible with CUDA 6.5. That does not explain the freezing behavior, but I mention it for reference.

The only suggestion I can think of would be to try the newest possible linux driver. I would suggest trying 340.46 from here:

http://www.nvidia.com/object/unix.html