i am running 10.6.2 and installed vSigX.app . working ok.
I wonder if you really mend ADAT and not FW (FireWire) . Of cause, ADAT is running if your sound card is offering ADAT .
FireWire support is not there yet in EventideOS 5.3 connecting to Mac OS 10.6.2 , so running and connecting the H8000FW to a Mac via FireWire has to be under Mac OS 10.5 .