I had a similar problem a short time ago, it may not be the same problem you are having but worth a shot.
Load up the software that XM came with, and try to listen to one of the stations. If none of the stations come up, it is a USB problem like I had. I had to disconnect the XM from the USB port, and reconnect it and have windows re-detect it. USB still sux, and is not perfect by any means!
I have actualy spent many hours trying to get something USB to work, only to unplug it, and plug it into another open USB port and work. This should not happen, but it does, as many people can attest to this I'm sure.
My GPS receiver still refuses to work on one of the USB ports on the front of the PC, but works fine on either of the 2 ports in the rear, even though my USB keyboard and touchscreen controller work on the front ones.
Definately try to see if your XM software works before trying to determine if it is a RR ussue or not.