I had A/C put in our house this past summer(2008),which worked great. Come around October I closed off all room supply vents and the main return leading to the air handler located in my attic/crawl space. About a month or so later(Nov) I took notice that my thermostat wasn't displaying the temperature. Through further investigation I found condensation inside the air handler and pull box, which tripped the breaker...hence no thermostat display. I had a new roof put on 5yrs ago, the roofer says it's not a roof problem. Each room vent has a rubber gasket to seal and the main return has a piece of rigid insulation to block hot air from getting up inside. This can't be right? What about mold when I turn the system back on? Any help or advice would be greatly appreciated!!