Ok, turns out the magic trick to getting the Lucent FW323 Firewire card to work is to load the raw1394 modules before the ohci1394; then all of a sudden the gscanbus goes nuts dumping data and dvgrab gleefully grabs frames.

Now I have a different problem: Is there no software that will read the output from dvgrab? the README says how to capture a movie file, but then says "go get windows media player"???? Ok, I expect there is a deep reason for that, but since that's not an option around here, it's back to google to see what my alternatives might be.