Sounds to me like you need more case ventalation. One 80mm fan is not very much. When you say you it works when you put your house fan on it, are you taking off your case's side panel? If so I would be willing to bet that you simply need more case ventalation. Perhaps your ram or some other component is overheating... something sure is.
You sound somewhat screwed as far as case fans go though. You may want to look into getting a cheap case that has both front and back ventalation, the larger the fans, the better. Other than that, try adding another 80mm fan, and make it so that one is blowing in and one is blowing out.
EDIT: A case with 1 120mm fan in the front, and 1 120mm fan in the back should provide adequate ventillation. The cheapest ones like that on newegg are $60, I'm not sure how much you can spend.
Yes, but no sprinkles. For every sprinkle i find, i shall KILL you.