SET WITHOUT OIDS and VACUUM badness?

This is what we did:

0. BEGIN;

1. ALTER TABLE ... SET WITHOUT OIDS

2. A bunch of things are selected out of this table and inserted into 
another (using INSERT ... SELECT)

3. An index is created on a timestamp field on this table

4. Then there's an update on a related table, that selects stuff from 
this table.

5. Renames a column

6. Drops a constraint

7. Adds a foreign key

8. Drops 8 columns

9. Drops 2 indexes

10. Drops 3 triggers

11. Then a tsearch 'txtidx' field is updated, and then cancelled halfway 
through

12. ROLLBACK;

13. VACUUM FULL forums_posts;

Then we get thousands of these:

WARNING:  relation "forums_posts" TID 22763/10: OID is invalid
WARNING:  relation "forums_posts" TID 22763/11: OID is invalid
WARNING:  relation "forums_posts" TID 22763/12: OID is invalid
WARNING:  relation "forums_posts" TID 22763/13: OID is invalid
WARNING:  relation "forums_posts" TID 22763/14: OID is invalid
WARNING:  relation "forums_posts" TID 22763/15: OID is invalid
WARNING:  relation "forums_posts" TID 22763/16: OID is invalid
WARNING:  relation "forums_posts" TID 22763/17: OID is invalid
WARNING:  relation "forums_posts" TID 22764/1: OID is invalid
WARNING:  relation "forums_posts" TID 22764/2: OID is invalid
WARNING:  relation "forums_posts" TID 22764/3: OID is invalid
WARNING:  relation "forums_posts" TID 22764/4: OID is invalid

This seems to be reproducible...

Chris