I saw this thread before I left the house (running late) and knew it would be the neutral wire in the wrong place. Being I am on the west coast, I have had many a home owner call us after hours east coast time trying to hook up there own spa because it keeps tripping the breaker. 98% of the time its the wire, funny though most people think they bought a psc o chit spa and quite pissed that it doesn't run, and quite humbled when they find out they hooked it up wrong.
I have also talked to and argued with many electrician that can't wrap there mind around the fact that Jacuzzi and Sundance don't need a neutral wire ran to the spa.