Looks like you've had as many problems getting 2 clients running as I had trying to get 2 X 9800GX2s running.

Some basics that need to be covered... Different machine IDs on each GPU2 client? Vista 64 requires a monitor or VGA dummy plug with desktop extended at all times. You can't unplug it like XP. RivaTuner needs to see both monitors always. If it asks for a reboot for detection, reboot. If RivaTuner doesn't see 2 monitors you will not be able to OC the GPUs separately. This was my major hurdle in first getting 2 GPU2s running at the same speeds. HTH. Good luck!