Well, before reading this, I got up there (roof mount) and cut 15 or so feet off the cable and redid the connection. Of course the HD channels work great (as they always do ... AT NIGHT). I didn't check my voltage up there, forgot the meter at work.
Yes, it is RG6, HOWEVER it is really crappy RG6. Only about 10 feet of the cable is outside of the house.
Could it be the crappy cable? or is it most likely the LNB. I'm one of those people who hate to spend $150 when it could be fixed with less. However, time after time I end up spending the $150 after the other things don't work ... this does have the added benefit of upgrading your equipment, etc. fairly well