Hi Martin,

The MINI's are notorious for doing this. It appears that there is a grounding problem with the AUX connector mode on the head unit that causes the problem. My AUX input was doing the EXACT same thing (i.e. disappearing as an option/mode from the head unit) until I installed a simple ground loop isolator. I picked the isolator up from RadioShack for $16.99 (part number 270-054) and wired it inline with the AUX input. Once the isolator was installed, I never had the problem again.

BTW, on my car I could also temporarily work around the problem of the Aux mode disappearing from the head unit by simply not inserting my audio device's connector all the way into AUX input.

Weird...

I hope this helps some.

-- MIKE