Black MacBook WiFi drops when fan starts blowing
That's quite an odd issue.  I would suggest re-installing OS X Lion and seeing if that rectifies the situation.  If that doesn't fix it, I'd take it to an Apple Authorised Service Provider (AASP) or an Apple Store - sounds like either the AirPort card or the Main Logic Board in that unit is faulty.  I wish I could look at that unit personally, I'd love to find the root of that issue.

Good Luck!