im having the same issue. i think it is the white plug that goes into the back of the unit, not the ipod cable itself. I took the unit out and it seems like the ground wire (black) is a bit loose for the right front speakers.
I just finished installing the update on my 700bt and I can no longer turn the beep completely off. even with the master volume all the way off, I can still hear the beep. Anyone else have this issue?