WARNING: owner of type appears to be invalid?

I recently installed postgresql 7.1.1, and now when I run pg_dumpall
(which I do in a nightly script for backups), I get the following
messages, duplicated for each database in the system:

WARNING: owner of type 'pg_inherits' appears to be invalid
WARNING: owner of type 'pg_index' appears to be invalid
WARNING: owner of type 'pg_statistic' appears to be invalid
WARNING: owner of type 'pg_operator' appears to be invalid
WARNING: owner of type 'pg_opclass' appears to be invalid
WARNING: owner of type 'pg_am' appears to be invalid
WARNING: owner of type 'pg_amop' appears to be invalid
WARNING: owner of type 'pg_amproc' appears to be invalid
WARNING: owner of type 'pg_language' appears to be invalid
WARNING: owner of type 'pg_largeobject' appears to be invalid
WARNING: owner of type 'pg_aggregate' appears to be invalid
WARNING: owner of type 'pg_ipl' appears to be invalid
WARNING: owner of type 'pg_inheritproc' appears to be invalid
WARNING: owner of type 'pg_rewrite' appears to be invalid
WARNING: owner of type 'pg_listener' appears to be invalid
WARNING: owner of type 'pg_description' appears to be invalid

Does anyone know what's causing this, and how I can fix it?

- Marc