[crysis]

Hi,
i also have this problem, an auto electrician friend of mine tells me it is a faulty head unit, apparently when you turn the key in the ignition the head unit sends a signal to turn on the rear amplifier to the cars computer...... that is now not happening because the head unit is faulty, this fault is also causing the front speakers to act eratically, he also says that the only way to prove this is to have an official Audi diagnostic, as the standard machines will not Pick up a fault, i have not got around to doing this yet............. hope that helps