I find that OS9 can't write metadata to FAT32 formatted disks. Two possible fixes:
1. Format your FireWire drive on the OS9 machine as a HFS+ disk
2. make a read write disk image on the firewire drive from your OS9 computer, copy all the data you want to transfer to the disk image, and then dismount and remount the disk image on the OSX computer. That way you won't lose metadata and won't have to resort to reformatting the drive.