Originally Posted by Bokehboy
Oops, my bad.

Right you are so I edited my post to "aperture" blade.
The lens is still under warranty from Sigma so I would prefer to get the warranty work done first. They have several authorized warranty shops in the U.S.A. so I guess I should ask if anyone has experience with any of their shops.
You may be right though. Sending it back to Sigma may be the best bet.
Thanks for your help. I have never had to do this with any lens before so I am a newbie to this type of issue.
Being in PA, just send it to Sigma in NY. I sent a DP1 to them and the turn around time to SC was surprisingly fast. They even replaced it instead of repairing.