Capturing HDV on external drives

I'm capturing HDV from an HDR-FX1. Sometimes, if I try to capture directly to an external Firewire drive, the capture will stop and I'll get a message saying "the program cannot communicate with the deck....etc". It will actually start capturing and then it would do that, after a minute. In this case I've had the camera hooked up to the front Firewire port of a Dual 2 GHz G5 and the external Firewire drive to the Firewire 800 port in the back. If I switch the preferences and I tell it to capture to the internal SATA drive, no problem.

On the other hand I have another Dual 1.8 and I'm capturing through the FW800 port on the back and storing it immediately on an external Firewire 400 drive. And it captures fine.

Stumped. Any ideas, why in one case it "crashes" and it won't capture and in the other case it captures fine?

The two/three FireWire ports on a G5 are managed by one pile of electronics inside the machine and will interfere with each other. To get *separate* high speed connections, you need to put a PCI FireWire card inside the machine and split the devices--one on the card and one in the machine.

Koz