Yea, you've gone through what I would have done. Looks like you're going to need a PCI USB hub, or I suggest you check the USB connectors on the motherboard, and the condition of the wires, and such. Flip the configuration of the pins if necessary, experiment around.

Check your Motherboard USB headers and also check your motherboard and Case manufacturers documentation.
connected to the board.

Result - I just left the two case ports and
I experienced a similar problem until I discovered that the Motherboards USB ports wont work when the Case USB ports were purchased a 4 port powered hub which i plugged into one of the ports on the rear of the machine.