thank you sygnus21,
my last solution is to go the store and replace my card.
meanwhile i'll try my best to fix it myself, i listen to your advice and i don't want to lower the clocks. if it's not work with the clocks that came from the factory, so it's a faulty video card.
what i'm going to do, is to clean up the card from dust and maybe increase the fan speed manualy, maybe it's only a problem of high tempature.
i'll update if i will succeed in what i'm going to do.
thanks for all the help
hope to find the right solution for me eventually.