So I am driving to work today and all of a sudden my XM starts to fade out, kinda like you are going by a tall building or under some trees. I also have Sirius in my car running through the AUX jack and it was fine. The funny thing was that the radio still was getting artist info and tunning to the channels. I could even see the artist switch, just no sound. When I got to work I turned the car off and back on and it was working again.

I had that happen with the Roady2 that was installed in my Corolla a couple of times. I found turning it off and back on usually fixed the problem.