I would recommend replacing to co ax cable between the dish and receiver with 100 grade cable. There is ct100 and qf100 available. If that dont solve it, have the alignment on the dish checked, try replacing the lnb and if you could get some 1 to lend you their receiver and try it, as it could be a faulty receiver. I have seen it cured by replacing the cable so do that first.
Terry
May 2008