Forum OpenACS Q&A: Response to pg_dump moves datamodel but not data: 7.0.3 to 7.1.3-4
There were indeed several switches between the postgres and nsadmin users in my dump file--notably from the lines that created all the tables (as nsadmin) to the ones that inserted the data (as postgres). pg_dump was barfing on the switch. (Note: this was a dump file created with the -d and -D flags.)
Mystery solved. Thanks for the direct help, Don, and the indirect help, Pascal!