error while vacuuming

I try do vacuum a database:

[PostgreSQL 6.5.0 on i686-pc-linux-gnu, compiled by gcc egcs-2.91.66]

type \? for help on slash commands
type \q to quit
type \g or terminate with semicolon to execute query
You are currently connected to the database: ecoscan

ecoscan=> vacuum;
ERROR: Index pg_temp.3920.1 is not a btree

Any hints? Is it possible that the creation of temporary tables with
indexes clashes vacuum?

Thanks Herbie

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Herbert Liechti E-Mail: Herbert(dot)Liechti(at)thinx(dot)ch
ThinX networked business services Stahlrain 10, CH-5200 Brugg
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~