It's not uncommon for a print organizer PSET to have an invalid file, especially in large plan sets. Something (drawing or model) got moved or renamed, and the PSET did not get updated. When that PSET is run though Print Organizer, everything goes fine until PO just quits. There will probably be some sort of error message in the Message Center, but it will probably NOT tell you what file caused the problem.

It would be very helpful if Print Organizer produced some sort of print log, especially for errors. Even just an error log would be extremely helpful in cases such as this.