I see. You haven't mentioned whether the Crystal case has its own power supply. It should have for USB operation; the standard Max power available at the normal USB socket is not enough to drive a HDD.
Firewire with 6 wires would do it, however.
Excuse me if this is a cheeky question, but, you're not using both USB and Firewire at the same time are you?
Firewire alone plugged straight into the MoBo is my favourite with my La Cie external HDD. But I've got three other external HDD enclosures. The Miglia enclosure for 2½" drives is great on Firewire with a power supply.
Another is by Amacom (USB is preferred) and the third is unbadged "cheapo" but made by Sanmax in the US from a chipset produced in UK called Genesis 711 that is similar to the Oxford chip you have (Firewire only).
You may draw comfort from knowing that there are others in the same pickle. Read
HERE
The clue that something is odd about the Amacon and Sanmax enclosures is that when I try Partition Magic to manage the Partitions, it will not play. Doesn't like them.
My La Cie, however, is as solid as a rock.
Lastly, the Belkin card may need an internal Molex power extension if you are asking it to drive a HDD enclosure.