When I first signed up with E*, I had 5 311s. Once a week one of them did what you're describing. I replaced cables, LNBs, switches, connectors, ground block, etc and the 311s still showed the acquiring satellite signal or the black screen of death from time to time when you turned them on.
I gave up and began replacing them all except for two of them and they still do it from time to time. All the other different receivers that I have don't do it. (625, 211and 501). I just learned to live it with and showed everyone how to reset them.
I wish I could give you an answer or solution but I've never been able to figure out why the 311s do that. Good luck!