This is specific for the used Oxford chipset. By default the case is setted to JBOD, but with JBOD you must use two HDDs. You have to set the chip to "Dual Sata". After that the HDD will be recognized either by USB or by Firewire.
Please install the setup tool from the included CD (you need installed Java in order to start this tool).
Connect the case via Firewire. From the setup tool (Upload/Upgrade configuration) load the configuration file "PI-083 Dual Sata" from the folder "UFW924DS".