my aura headunit has been behaving like this recently. i hadn't driven the car for a few days, when i did finally start it, the radio was asking for the code (it had been working fine for the past year). i put the code in and it worked ok for a day or two then it happened again when i switched it on. this carried on for a few days and i was about to rip it out and chuck it in the bin. Also, i'd turn the radio off and the sound would go for about 5 seconds but the radio wouldn't turn off, then the sound came back. I tried removing the face plate with the 6 buttons before turning off the ignition and its been fine ever since. i just have to remember to remove the face plate every time i turn off the ignition. I have an old sony cd headunit which may find its way in soon though.
