Using Roland GAIA (USB) and Focusrite Saphirre (Firewire)

In Cubase studio 4 I have a Focusrite Saphirre (Firewire) sound card with midi ports running into 2 hardware synths via midi cables. I also have the Roland GAIA plugged in through USB. Both devices appear in the Cubase Midi device settings and playing notes, moving knobs on the GAIA registers in Cubase and records. Problem I have is outputting midi back to the GAIA through the USB connection. It just doesn’t work. It works fine If I use the midi cables on the GAIA and include it in the chain of midi cables but no way with the USB interface. All drivers and firmware are up to date. Anyone have any ideas would be grateful.