I have a 2006 w/ nav and sometimes after I start up the car, the XM or radio doesn't turn on. Nav works fine and I can flip over to the audio screen, but it doesn't show anything. hitting the xm or radio buttons doesn't do anything either. it usually goes back to normal if i restart the car, but sometimes it takes a couple of tries. once it does come back on, it works fine and never cuts off or anything. Any idea what could cause that?

fyi, i have installed dom's box in the trunk and don't know if i messed anything up. just trying to get an idea of what it may be before i really get in to troubleshoot.