Not sure what type box you have, but iof you got the 5LNB you have most likely got HD package, so I'm assuming you have an H20 Receiver. This happened with a replacement H20 I received, and after going through TONS of tweaks & tricks with D* Techs, and after 2 hours on the phone, they deemed the box defective. They immediatley sent me a new one.
IMO the H20's have too many problems and should be recalled & replaced. If it's not too late, (first 30 days) (might want to threaten cancelling since its ok for 30 days w/o contract pay out) and tell them you want to upgrade to DVR, and get the new HR20, you should get that free as a new sunscriber right now, but I could be wrong.
If the box is ok, then it's possible the installer did a crap job on the dish install.