Looks like the OBC functions are tied to the radio/MID. If you have problems with the radio then that's probably it.

If you search some threads with people installing aftermarket radios, they all talk about losing OBC functionality. It still calculates but can't reset anymore.

Like this thread that's on the very first page of the forum.

http://www.xoutpost.com/bmw-sav-foru...installed.html