John, your experience is similar to one I am having, and I’m thinking I may have fried a firewire port. I attached my ADVC-300 analog-digital converter device into the same computer I have used it with for the past 4 years, and the computer failed to recognize the device. I then connected my video camera to the same computer and it was instantly recognized.
I contacted Canopus tech support and they sent me some tests to run to determine if the ADVC-300 was damaged. The test results indicate it is in fact damaged.
I was not aware of the grounding issue with firewire until reading here, but I see now that in Canopus’ instructions they tell you to turn off the camera, ADVC-300, AND the computer before making the firewire connections. They don’t explicitly mention grounding issue, but it seems logical that is why they recommend powering everything down.
If you decide to hook up your camera to your computer, you might want to follow Canopus’ advice and turn off the computer and camera before connecting.