Hi. I do Bell and Shaw installs. Been doing it for 11 years.
I read this thread with interest, because I had a similar issue with a Bell dual-tuner receiver at a customer's home.
I was at the guy's house three times, and I coudn't figure it out.
Tried new cable ends, new LNB , same intermittent problem.
Then, I thought about the receiver itself.
So I went home, got my Bell single-tuner HD receiver and hooked it up at the customer's home. I told him to use it for a couple of days, while I took his home.
My receiver ran flawlessly on his dish & cables.
His receiver continued to have the same intermittent signal problem at my house.
Conclusion - bad tuner in the receiver.
The cause of Ralphy670's problems is, IMO, a bad tuner in one receiver. It is causing electrical issues within the coax cables, causing the LNB to get messed up, which in turn is affecting his second receiver too.
Take one receiver offline for a day or two, and monitor the behaviour of the 2nd receiver.
If Receiver #2 is working flawlessly, then Receiver #1 requires replacement (or vice-versa).
Good luck, and please keep us posted on your progress.