Quote Originally Posted by Ian Grant View Post
You should be able to cock and fire the shutter by bypassing the bodies mechanism, taht will tell you if it's the shutter or camera.
To be more explicit, in case the original poster has as much trouble figuring this out as I did, what the body release actually does is activate a little linkage that pushes a lever mounted on the bottom of the shutter (on the left-hand side as you face the camera). Even if the body's interlock is misbehaving, you should be able to poke this lever directly to fire the shutter.

It took me a LONG time to realise this, at the cost of a number of nice shots while I struggled with a balky body release! You may be quicker on the uptake than I am, but I thought I'd share the details just in case... :-)

-NT