Yup make sure to clean out all the dust. Your case should have pretty good ventilation after all so that shouldn't be the issue unless you did something weird with the fans. You can also go into catalyst control center, unlock, and then manually increase the fan speed to 70% or so to help keep temps under control. If you have a reference board then setting it to 100% may be a bit too loud for you, but I would set it at 100% if I was worried about the overheating. For some games I do that for my two 5870s, but of course my gigabyte UD cards are a little quieter than the reference design.