There appears to be a bug with FCPX when sending jobs to Compressor. The problem you described sounds similar to issues discussed in this thread: https://discussions.apple.com/message/16261001#16261001
Hi Keeber, yeah also have a look at this post. There's a detailed procedure in there to restablish CLuster and QMASTER using Qmaster 4 and Compressor.app V4. I have FCP 7 Suite installed on another filesystem and OSX so I dont know about the ramifications of having QMASTER 3.5 living in the same tent as Qmaster v4... I only have FCPX, Compressor 4, QMASTER 4 and Motion 5 on my production system...
anyway try this procedure in this post.. worth a look.
post your results for others to see.