problem w/ firewire over hub/repeater

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I'm having a puzzling problem connecting to a firewire digital camera, only
thru a hub or repeater, and only w/ xp. This was working fine on my computer
until I upgraded to xp from win2k, and still works as long as I use a direct
cable. It also works on another computer running W2K thru either direct cable
or hub/repeater. I don't know much about firewire, and I don't really have any
idea why a hub would prevent this connection from working for xp, so any kind
of wild speculation might be helpful.
thanks
dale b.

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