BMW X5, no reverse

I have a 2001 BMW X5 (auto trans ...of course).The factory stereo has been removed ,I installed another after market one .I ran all of the stereo wires down to the rear of the car and plugged them into the factory stereo wiring ,using the factory amp. Since then the car wont select reverse ,electronicly the car thinks its in reverse as mirrors tilt down ,reverse bepper activates ,but it just sits there idle .All other gears work fine. The navigation was removed ,and I pluged it back in ..but still no joy . It came with a Clifford Avantguard 5 alarm .the engine start has been connected .I have played with the remote trying different things but still no reverse .Unfortuantly I have no manuall. Is it possible that the stereo has affected this fault? ,or could it be the security system. Any help will be greatly appreacted .

Sounds to me like a trip to your local BMW dealer is in order... Personally, I don't think that your system did it, and you say everything "functions as though it IS in reverse", mirrors, beepers, etc. Hate to tell you that, but I think you're stuck with that "option"...It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."