Autovacuum tables missing?

Dear List,
Possibly this has been posted on this list already before, but I got the
following error when opening the properties dialog in pgAdmin III:

ERROR: relation "pg_autovacuum" does not exist
LINE 1: SELECT * FROM pg_autovacuum WHERE vacrelid=17241::oid

This is a freshly installed PostgreSQL 8.4.1 (downloaded Windows Installer;
Visual C++ compiled) on Windows XP SP3
Server properties say Autovacuum is running...

This sound familiar to anyone?

Rob