Thanks to both Paul Berkowitz and John Delacour! The files, as Paul said, 
had lovely bizzare names (but ending in ".txt"), and as John said, were 
being made in /tmp. Maybe it's a "version thing" (10.3.9 here)? Anyway, 
John's version, which takes control of the file name, works great for me.
Thanks.

   - Brian Johnson, "dryless in seattle"
     (prompter thanks delayed by digest mode)