BUG #2850: Cannot select from information_schema.schemat

The following bug has been logged online:

Bug reference:      2850
Logged by:          Tony Marston
Email address:      tony@marston-home.demon.co.uk
PostgreSQL version: 8.2
Operating system:   Windows XP
Description:        Cannot select from information_schema.schemat
Details:

If I am logged on as a user other than 'postgres' and I try the query

SELECT * FROM information_schema.schemata

I get no results. Yet if I try the equivalent query

SELECT * FROM pg_namespace

I can see all the available schema names.

Why is there a difference when the two queries are supposed to provide the
same results?