i have a 2011 328I Convertible and i had problems with the IRDIVE unit not responding.
basically i tried changing it and it didn't work. so here is the best way to fix it.
take it apart and resolder the pins on the main connector, and clean the board while you have it open. this is the cheapest way to fix it, and you don't have to take it to the dealer to have it programmed. it took me two hours from start to finish.

you can find some videos on youtube on how to disassemble, and the rest is easy. good luck