pg_dump adds the foreign key constraints after the data is COPY'd into the tables. So you might try dumping/restoring some small examples to see if you can correct the problem.
Did you have any problems reloading the dump? Did you edit the dump file at all before reloading it? Did you use any switches to pg_dump?
I dump and restore my PG 7.0-based site all the time, and have never seen this behavior (I dump my live site to load into my development site for testing changes).
There were some strange things with referential integrity and permissions, i.e. with different permissions on the referenced and referencing tables, but I can't imagine you've stumbled down that path . Not by doing a dump/restore...
