I've got the same problem, have tried all of your suggestions and still the problem persists. Stuck on 34% export every time, and then that error message.
I have literally done nothing to do with "compressor", have never downloaded it, have never made any changes to it.
I *cannot* update my OS any further until there is a known fix for the issue with newer OS having windows NTFS format issues resolved - i.e. under a newer OS, I cannot transfer files larger than 4gb to a USB stick even if I use disk utility to format that stick to windows NTFS. This means no more watching hi resolution movies in my lounge. I'm not risking upgrading. Ever. Until that prob is solved.
Thing is, I have done nothing to create this error in FCPX - it's inexplicable, came from nowhere and now I'm stuck with it... any other ideas?
UPDATE: Upgraded Compressor to v 4.1.1. Prob solved.
Rhetorical question - Why does FCPX not have more accurate and helpful error messages?
ronny courtens wrote: Hi Murray,
Happy to hear you have found the cause of your issue, and thank you for posting the solution.