In my experience it has always been a bad piece of data. I would have to take out a section at a time until I found the section with the bad data and correct it.
I believe that pubtex is part of the Print Composer process for making PDF. If you can run Print Preview, the Print Preview process may create a DVI file that is viewable up until the point of failure in the document. This may give you some insight into the markup or content that is causing the problem.
Also, you can create a PUBTEX_FORCE_LOG environmental variable which is used to save formatting errors for later examination. Setting the value to yes will create a log file which can be supplied to PTC Technical Support<">http://127.0.0.1:65330/aeHelp/help7573.html> to troubleshoot formatting problems.
I can't remember whether any of the pubtex errors I saw were content-driven. I think they always required a fix or some sort of workaround provided by support.
Even if it turns out that you have "bad" content that is somehow causing this error, PTC definitely does not like that sort of failure. So even if you are able to find a workaround or a fix by removing / fixing your input, PTC support (and ultimately the rest of the hive here 😉 would appreciate your opening a case with them so they can chase down the problem and fix it even if that just means a more graceful exit and providing a helpful error.
