Beyer Dynamic RSX700 reception problems

I just bought a pair of BeyerDynamic RSX700 wireless headphones after reading several great reviews. The sound quality is excellent provided I stay within 5 feet of the receiver! As soon as a stray more than 6 feet away (on any channel) I experience audio clipping similar to VOIP when that clips. I have moved the receiver to a couple of different locations but am restricted to length of cable to the amp. I also have a PS3 working wireless to my broadband and my home PC is also wireless as I live in an old house that requires it. Could this be the problem? Help from the community out there please!

Jim