orphaned trigger

This is in 7.1.1:

I was playing around with a table called user_comments and then dropped it.
One of its columns referenced the user_id column of another table, users.
Now whenever I try to update users, I get results like this:
bf2-new=# update users set last_visit=sysdate() where user_id=4; ERROR:
Relation 'user_comments' does not exist

Somehow a constraint trigger that should have been dropped wasn't.

I looked at the dump file and this is the only reference to user_comments:

CREATE CONSTRAINT TRIGGER "<unnamed>" AFTER UPDATE ON "users" NOT DEFERRABLE
INITIALLY IMMEDIATE FOR EACH ROW EXECUTE PROCEDURE "RI_FKey_noaction_upd"
('<unnamed>', 'user_comments', 'users', 'UNSPECIFIED', 'user_id',
'user_id');

but I am not out of the woods here because it won't let me drop it:

bf2-new=# drop trigger RI_ConstraintTrigger_44349 on users; ERROR:
DropTrigger: there is no trigger ri_constrainttrigger_44349 on relation
users

It's in pg_trigger all right -- and with tgrelid = (select relfilenode from
pg_class where relname = 'users') -- but it won't drop.  Would manually
removing it from pg_trigger cause Bad Things to happen?

-Jonathan