beeping i dont know, but maybe your permanent live and your switched live are the wrong way round, or joined together even. It's not a bad thing, but it would explain the stereo not going off with key.
Or perhaps it is related. If there is no switched live there at all, it could be that when you are turning it on manually, the stereo will be on a timer, and maybe beeping before it goes off. If you are having to turn it on and off manually, try timing the interval between on, and the auto turn off.
Darrell
February 2010