I hooked mine up yesterday with one line and had no problem at all. It was a little slow in running through the setup processes, but came out working perfectly.
Here's what I did.
First went to the point the dish step. Manually ran the switch test. It looks for both. It finished showing INPUT 1 all OK and INPUT 2 having a problem. But it allowed me to exit the screen. Then I went and set up my HDTV display options and went to exit out of the menus.
At that point it went into its 5-step initialization, which took several minutes. Then it did a EPG load. After that I had my EPG with the 100, 101, and HD Demo channel all working. I then called into Dish and the tech told me that a 942 would not work with only one input. I told him it was working fine and I was viewing the HD Demo channel as I spoke to him. He was surprised. He then activated my receiver and all of my channels came in normally.
No problem.