If the recent update does not help
try this recommendation from Technosavant
I did this update same day sirius xm update came out.
Have not had the on going problem with channel updating since.
Download page with software update for the RER (note: NOT RHR):
The 2.402 is the most current software revision and should not only fix the "updating channels" issue (fixed in 2.401) but also improve iPhone 4 compatibility. Download the file, burn it to disc (piece of cake in Win Vista and Win 7), then stick it into the disc slot on your head unit. It will load the disc and begin the update automatically. I'd recommend you do this with the engine running (should only take 5-10 minutes or so). There are a couple prompts you will need to OK as things progress, but it generally does everything itself. You may need to re-pair your phone to the unit when finished.