Problem setting custom auto-vaccum settings

["Benjamin Krajmalnik" <kraj(at)illumen(dot)com>]

I hae a set of tables which are quite large and which only have records
inserted into them.
The size of the tables (which are partitioned tables) reach 2-3GB (data
only) plus indices.

I decided to exclude them from the auto-vacuum process, since I
identified that I was having performance issues when these were being
autovacuumed.

I went to the vacuum settings tabs, clicked on the "Custom Settings"
checkbox, and unchecked the enabled checkbox.
So far so good.  Pressed OK, no error.

Now, if I try to make a change, I am getting the following error:

Column "base_scale_factor" of relation "pg_autovacuum" does not exist.

I am running pgAdmin 1.4.2 against PostgreSQL 8.1.4, both on Windows.