I was coming to say I was having "failure to start on nodes arbitrarily with RC6"I am using it for production if you keep an eye on it you close and restart these servers one or two times and it will eventually render on them, it is an inconvenience but at least no black frames :)
they just say waiting for render to start on the render node machine, if you close the dr server and open it again once or twice it starts rendering. I will send a log tomorrow from work. Thanks