Suddenly nothing but noise

We have owned a Sennheiser RS 120 wireless headset for five years. It has always worked perfectly until three days ago. We now get nothing but noise. 1.) We have tried the system on 3 different TVs and the cable box, always just noise. 2.) The green light, indicating a source found, is always on. 3.) We have tried all three channels on the transmitter. 4.) We bought a brand new RS 120 and tried all the same things, and still nothing but noise. (We returned it). 5.) We tried the reset procedure (disconnecting, taking out batteries) to no effect 6.) We do not use a power strip for it. 7.) We have no new electronic devices in our home, only things the RS120 has been working with for years. Any ideas, Gang? Thanks.