There has not been any analog TV broadcast since June, 2009. If his issue just showed up and he had the full spectrum of stations before than it seems it's probably that TV preamp he metioned.
His unit is analog, I looked it up. It will not receive any digital TV signal. I was actually surprised to find there was any place in the US that had analog TV transmission, but I guess there a few left, until the FTC put a stop to them. He needs a Tablo like you have, they look a really good unit.
I think what the antenna cable is connected to makes a difference, and I bet not all are created equal, especially in terms of error correction. So, when the OP upgrades, he should not go cheap.
