Laptop cooling fan stops suddenly, after a period of use.

I'm having this problem for a long time. The cooling solution (single fan for CPU and GPU) on my LG 590 (5700) laptop, suddenly stops to work and don't start again causing overheat and consequential system shutdown to prevent damage.

How can I solve this?

[I'm using Ubuntu 12.10 but the laptop was originally designed to run Windows.]

- The fan works normal on Windows. It doesn't stop cooling even under heavy load such as games or full hd videos. As the processing temperature increases, the rotation rises too. In Ubuntu it happens in reverse; when under heavy load it just stops spinning;

- I always use the latest stable driver version of graphics card;

- lmsensors are installed and working. No luck with fancontrol though. When I try to configure it, I get: "There are no pwm-capable sensor modules installed".