Have you got the card overclocked? if so try slowing it down, if not overclocked then still try forcing it down slower than specs, you will probably find that it will run ok a little slower, but atleast it will get you by, there are the 2 sliders the GPU speed & the Mem clock, move them both down a fair bit, try it out, if it goes ok then you just have to go back and tweak it to the best before it starts breaking down again.
Hope this helps.
