My best guess would be that your USB hub is an unpowered hub, and thus unable to meet the demands of the camera. Since the ports connected directly to your system are all powered, they work fine.
If your USB hub came with any kind of power adapter, make sure it is connected. If it didn't, you're either going to have to get a new, powered, USB hub, or plug the camera into a port located on the computer itself.
My Fuji 3800 will freeze my computer ( atempting to download picts) if the cable is pluged into my 4 port expansion but works ok if pluged in directly to the same USB port the expansion cable used in back of the computer. I am out of ports and would like to use my 4 port expansion port - Why is this and what can I do?