Cool to know that this combo works. I recall when I upgraded to the 1D2 that the SIGMA 500mm f/4.5 EX HSM worked great on it too, HOWEVER< the add the 1.4 t-Con to the mix and even though it SHOULD AF (sub f/8) it would not!
It does on the 1D though!
I have same exact story with Sigma's 70-200 F 2.8 (Older - non-chippsed swapped vesion) that works in all modes when attached to 1D Baba but gives lens error with any newer camera body including 5D, Tis, XT, xxDs etc.
Than old chips of Sigma lens is the problem and shame they didn't value their products for a permanent recall/Free rechipps that was started and ended long back.