I am researching this right now. I had an older FW400 drive with the Oxford bridge board running under Jaguar and after waiting a few updates to Panther, I moved it over to Panther and it caused the drive to mount once and disappear once and be unusable after that, even on the Jaguar system.
I wrote off that enclosure as bad and ordered another on to work on Panther. Now that I am about to go to Tiger I a suspicious that the first enclosure is not really bad, just needs a firmware update.
My concern is that using the new FW400 enclosure with a drive is part of the sequence I will need to use when moving from Panther to Tiger.
My question; is the firmware in this enclosures bridge board usable in Tiger or not? If you read MacFixit and other troubleshooting sites, you will pick up a thread about Firewire400 drives not mounting in Tiger.
I am investigating ways to verify what version of firmware is in each FW400 enclosure and what it needs to be for Tiger.
I don't think it is a OS issue. I have a Lacie 500gig firewire drive that keeps unmounting ever since installing Tiger. Although this happened a lot even under 10.3.8 & 10.3.9, this is sad to see happening under Tiger again. I think there is a major Firewire issue with certain G5's and especially with Lacie drives!!