Audio In on my 5dmk2 is not working :(

[Multi]

 Hi everybody, I got some strange problem since a couple of days, on my loved and trusted 5dmk2. I can not get any sound in anymore. with newest and older firmwares whenever I plug in a line In signal the camera does not switchh to the external source. In Magic Lantern the camera does neither get any Audio when I switch over to external stereo. I checked my Mixpre with my 7d and there all is working, so no cable probs...
Now do I have to send the cam to Canon service or is there a firmware trick to maybe get the In working again ? any others who experienced the same problem ?

Thanks for reading Matthias von Mutius, Bavaria based film and tv storyteller

[Malcolm Debono]

Make sure that audio recording isn't turned off from the Canon menu.

Also, does recording work with the built-in mic?