Alienware m17x r3 with GTX 580m low clock issues

Hi, recently i've been having some issues with my graphic card...

(Currently: Alienware m17x R3, with Nvidia GTX 580M, Windows 7 64bits)

First, like a month ago it started throttling, and after some researches, i have discovered it's normal and it always happen when the gpu core temperature reaches something around 76ºC (it just lowers the clocks to something around 30% of it's capacity until the temp reaches 50ºC), and when it became too constant (like happening every 5 mins) i thought it might be a problem like overheating, so i'm already ordering some arctic cooling paste, but today, for some reason, all the clocks bugged to something really awkward (like the gpu memory clock, which was put into 67Mhz)...

Restarting/reinstalling stuff won't work, i already tried overclocking to 'preset' clock, but it also didn't changed anything, it's like it's locked at this clock rate somehow, how do i proceed?

(warranty already run off etc, so that's why i'm here)