Not sure if you had fixed this. I had the same problem and solved it like this:
1. Remove the lens.
2. Take some lighter fluid and a small paint brush.
3. Dampen the brush with lighter fluid
4. Brush the inside of the lower shaft.
5. Do this again on the shaft on the left of the mount.
6. Put the lens on.
7. Stop down the lens manually a few times.
8. Set the aperture on the lens at minimum.
9. With the shutter set to 1-2 sec, fire it and watch the aperture blades.