pg_dump failure: "handler procedure for language plpgsql not foun d"

I am attempting to do a pg_dump, preparing to upgrade to 7.1.
I have attempted a pg_dumpall, as well as pg_dump for various individual
databases, and each fails with the message "dumpProcLangs(): handler
procedure for language plpgsql not found"

Everything appears to be in place (see below), and I am stumped. The only
likely cause seems to be some new problem introduced when I recently
upgraded my OS (from FreeBSD 4.0 to 4.3-RC), and upgraded pgsql at the same
time (7.00 to 7.03: bugs were biting). Everything else seems to be
working...

I would be very grateful for any suggestions as to how to fix this.
TIA

template1=# select * from pg_proc where proname like 'plpg%';
proname | proowner | prolang | proisinh | proistrusted |
proiscachable | pronargs | proretset | prorettype | proargtypes |
probyte_pct | properbyte_cpu | propercall_cpu | prooutin_ratio | prosrc |
probin
----------------------+----------+---------+----------+--------------+------
---------+----------+-----------+------------+-------------+-------------+--
--------------+----------------+----------------+--------+------------------
---------------
plpgsql_call_handler | 71 | 13 | f | t | f
| 0 | f | 0 | | 100 |
0 | 0 | 100 | - |
/usr/local/pgsql/lib/plpgsql.so
(1 row)

template1=# \! ls /usr/local/pgsql/lib/plpgsql.so
/usr/local/pgsql/lib/plpgsql.so
template1=#