http://www.youtube.com/watch?v=MmflKM6Fb2E (f/2.8 so aperture is not visible)
I tried to fire the lens "manually". I just hat to push the release pin to the side. But again i couldn't see the shutter close, open and close again. It just closes once after the exposure time is over and stays closed then.
But i have read that you normally shouldnt try to "fire" the lens this way..
So i guess the problem is the lense