The first thing to try is to turn multi processing off or try rendering to an image sequence instead of a movie.
The second thing to do is to give us details about your project. What codec? Many are not working with MP on.
It renders OK with multiprocessing turned off. It's rendering to a ProRes422HQ Quicktime movie. It works perfectly well under CS6, with identical node settings (3GB per node, 3 nodes, 6GB free). Is there any other information I can provide?
Rendering to image sequences is something I try to strenuously avoid. I'll try and do a test with it later though, and see if it still brings up the same error message (and/or slow renders)
ProRez is not MP compatible but it seemed to slide by with CS6 most of the time. Even though QuickTime hasn't been updated for a long time there is an update for ProRez on the Apple site. Have you tried the update? I have not tried a MP render to ProRez for a long time because about 90% of my projects do not use MP compatible plug-ins and MP rendering kills the render times.
I'll try rendering to a different codec later. CS6 works fine with ProRes - always has done. I'm running the latest version of the codec too (installed with the FCPX updates). I can understand why there might be issues with codecs that use interframe compression (Like h264), but ProRes uses I-Frames only.
Although Quicktime hasn't seen a lot of love from Apple recently, they are still upgrading the codecs - and it is the default transcoding option for FCPX too!