There is a small LNB with two wires going out (one to each receiver), and a third wire coming out of a really large LNB looking thing (which I assume is the DirecPC LNB) since it has the transmitter thingy mounted on it too with a wire going into it. Sorry, I was wrong in my original post about having a separate LNB for each receiver, It is a single LNB with two outputs. So it sounds pretty much like I have a bad LNB based on your post. As I understand it, an LNB is a pretty cheap part and as long as I don't move the dish, I could probably easily replace it myself. I will come back and post whether it worked or not.

Thanks a million for the advice. I tried explaining this to the DirecTV support line but they basically troubleshoot with me until I get both tvs working (using the technique above), then they act like there isn't a problem and don't want to help me anymore.