Chris,

I had the EXACT same problem with my Sirius radio. In the end it turned out that the antenna itself had failed although it was completely intact with no signs of physical damage/wear. Went to a local electronics store and purchased a new antenna, plugged it in and 'voila' no more ACQUIRING/NO CHANNEL. I was told that with time some of the antennas just simply fail.

Hope this helps,
Charan