I have the problem that the fan of my ATI HD 4770 goes on and off contunuisly.
Besides the noise, the mouse and the keyboard is not working properly when the fan goes on. e.g. if I add a Textlayer in Photoshop I need to press the letter keys a couple of times before I can see it on the screen. I have the newest drivers installed.
Make sure your PC, and video card fan, is clear of dust bunnies etc then reseat the card and see if this resolves your issue. If you don;t monitor your temperatures I'd use MSI Afterburner or another software that monitors CPU,GPU and HDD temps.