My wife and I both have S50 units and 2006 x3's. My S50 is from last year January and hers is from this year December.

We both have BMW Installed AUX jacks. Her AUX vanishes at random and doesn't come back until the car is shut off and turned back on. The S50 is the onlything connected to the AUX.

On my X3, the same thing happens but less often.

This does not happen with our ipods.

I'm guessing there's some incompatability between SIRIUS aftermarket units and the radio in our cars.

I have yet to find a solution except to just install the fm adapter behind the radio.