Audio Systems: Cassette adapter E320 1999 for ipod issues, electronic beep, rf modulator

Question
I have an Bose OEM upgraded stereo in my 1999 Mercedes E320; the face plate flips down to allow insertion of cassette tape.   I bought a cassette adapter from Monster; inserted it and plugged it into my ipod.  It plays great for four or fives seconds then emits an electronic beep from the stereo through the speakers while the music is playing as if to indicate an issue; and sounds like the tape player is switching to play the correct side of the tape. The beeping continues intermittantly until the stereo stops playing a few sconds later.  Has anyone else had these problems? does anyone know what the solution is?  The sound is fantastic when it des play and I really dopnt want to step down to an FM modulator device to play my ipod in the car.

Answer
sounds like a bad adaptor; the reels inside take too much torque to turn them so the deck 'thinks' it's at the end of tape and tries to switch directions. i'd try another adaptor. and rf modulator being 'down'? in theory, the modulator has better frequency response and much less 'hiss', and better channel separation than cassette adaptor.