I am not speaking from experience here, because I never had the same problem.. I just played around with mine for a bit, when you start depressing the lever to cock the shutter it will just stay where you left it, you can wind in in tiny increments, only when you get to the end the lever comes back up. If it' s cocked, the mirror should be down. Also see if the mechanism that cocks the lens with its two pins is in the cocked position (cocked the left side (facing the camera) is up, and the right is down) if it's the other way round, (left down, right up) you could carefully try to cock it that way, maybe with two bobby pins, and see if that releases the mechanism. Good luck.