I personally don't know much about firewire, although I would 1st want to check on whether your drives work ok all by themselves ...
Troubleshooting often requires breaking things down to 'simple'.
Regarding my 'own' experiences with USB external hard drives not showing up on my Dell XPS Vista laptop...what I find is that although I don't see it listed as a drive in 'My Computer'...oddly enough, when I connect it & power it up, the drive actually automatically pops up a window in which I can then access it. I don't know why I can't see it 'My Computer'... but since it works anyway, I just deal with it the way it is. If I even need to copy/paste contents to and from, I wait for that auto pop up window...sometimes it doesn't pop up, I just start over, unplug & repower up.
In this possibly what you may be experiencing? ...with OR without that hub.