Build A Gadget has a support FAQ page, and you might try checking their troubleshooting steps for "No Sound" HERE
. They have good support...at one point, XM did an update to their online service which broke everyone's feed, but Build A Gadget was on top of it, and issued an update to their gadget in about a day, got everything working again.
I'm listening to Cinemagic (my favorite) right now through the gadget. I hope the link helps you to get your gadget working again.