Saving files in Freehand 10

A computer in an office I service is doing some strange things in Freehand 10. The machine is a P4 running XP. Sometimes, when a file is saved, instead of a Freehand file, it saves the file as a “5” or “04” file. The graphic artist knew enough to set up XP to open these files with Freehand, and can continue to edit them, but she cannot send them to anybody. Normally, she sends open files to the print bureau. She mentioned that she sometimes gets a notice referring to memory when trying to save a file, but I haven’t seen the error message myself.

What are 5 and 04 files, and what might be causing this strange behavior?