pg_dump question - index error?

Running PostgreSQL 7.2.1 on RedHat Linux 7.2.

I'm trying to do a pg_dump of a table and get the schema only and
I get this error after about 10 minutes :

[snip]

pg_dump -s -t test_table  -d testdb > /var/local/schemas/out_table.sch

pg_dump: query to obtain list of indexes failed: ERROR:  syscache lookup for index 3248834497 failed

[/snip]

I've never seen this message before when doing the same thing - how can I correct this?

Thanks!

-X