the same problem happened to me a few weeks ago. i was without any music for 2 weeks, its worse than one may think. but i finally took my car to a shop and they told me my sony receiver was straight fried. hopefully youre problem isn't that bad, but that might be it. i spent a lot of time taking my car apart looking for fuses and loose connections without finding anything. thankfully youre in a bimmer and driving is sometimes good enough entertainment. though traffic is pretty bad without music. good luck!