Had a look at the thread to get on the pace.
Just tested mine and it works.
About the gear used in this test:
Macbook Pro 17" late 2011, OS 10.8.2 using the Thunderbolt port.
Black Magic Intensity Extreme using BM Media Express V3.2.
Apple Thunderbolt cable.
Panasonic HDC-SDT750 set to 1920 x 1080i50.
HDMI cable mini to standard cable.
I've noticed that all connections should be made before opening the BM capture app or it's not recognized by BM Media Express. This applies the BM box rather than the camera.
Open the BM app and confirm from the Cascade Menu under DEVICE that there is a check mark against the model you use. Mine is Intensity Extreme with the tick indicating the device and the BM software are communicating.
Now setup your Media Express>Preferences to suit the camera and capture codec etc.
Note: If you don't see a bunch of options in the Project & Capture format fields to match your computers stuff then something is amiss.
Also you can check the MAC>System Profiler>Thunderbolt to ensure the computer is seeing the BM device.
Connect the camera and HDMI cable at this point if it's not already and switch on.
I'd suggest making all connections before starting.
Log and Capture in the BM software window should display whatever the camera sees.
You can either live capture or capture pre-recoreded clips as desired.
Hope this steers you in the right direction.
Al