How does it work just connecting with a single cable? BTW, it must be a CAT6. It can't be a CAT5 and expect it to work right.
Well I managed to get a much better result now. There were a few other issues that were fouling up the works, like Cubase choosing the default ASIO driver - which of course has appalling latency.
I will definitely want to try CAT6 though. I don't think the cables I had lying around here in the UK are. I have CAT6 cables back in LA. Maybe this will sort out one remaining issue I've experienced, which is that changing the tempo in a project causes the instruments on the Slave to glitch (audio pop).