ERROR: unrecognized object class: 1262 with 9.2.2 but not with 9.2.1

I recently upgraded from 9.2.1 to 9.2.2 and my unit tests for my application are failing when cleaning up my test database.

I am using the statement:

drop owned by wbjunit cascade;

at the end of a test suite to get rid of everything that was created during the tests.

Now since the upgrade to 9.2.2 it fails with the error message:

ERROR: unrecognized object class: 1262

I could easily drop and re-create the database, but I'm a) curious on how this situation could have happened and b) if there is a way to fix a problem like that with re-creating the database (in case this would have not been a unit test DB)

Is this a bug in 9.2.2 or did I do something wrong?

A "vacuumdb -f -v wbjunit" shows the following message:

INFO: vacuuming "pg_catalog.pg_depend"
INFO: "pg_depend": found 2 removable, 6219 nonremovable row versions in 47 pages
DETAIL: 0 dead row versions cannot be removed yet.
CPU 0.00s/0.01u sec elapsed 0.10 sec.

The "found 2 removable" part does not change, even if I re-run the statement several times.

My environment:
PostgreSQL 9.2.2, compiled by Visual C++ build 1600, 32-bit
Windows XP SP2

Regards
Thomas