I have the Sigma EF500 DG ST PA-PTTL for my DL and I saw the same bulletin. Said something about Sigma flashes NOT compatable with the K100D in SR mode or something. It went on to say that Sigma was going to issue a fix for it.
Actually they say that are offering a free upgrade for owners of the DG model.
"To overcome this, we will start supplying a free-upgrade service to our customers"