Dropping a database that does not exist

Hi,

I've been getting duplicate databases within my server. Dropping one of
them works, but when I try to drop the other, psql will say that the
database does not exist.

For example:

db1
db1
db2
db3
db4
db4
db5

Running DROP DATABASE db1 for the first time works and I'm left with:

db1
db2
db3
db4
db4
db5

Attempting to run DROP DATABASE db1 again will just give me "FATAL:
database "db1" does not exist"

Same scenario for db4.

I could ignore the error, but because of the duplicate database, I
cannot make a dump of the server.

Any one has any ideas why this is happening and how I can solve it? A
similar thing happened previously, but it was with tables within a
database. The only way we solved that was by dropping the database and
recreating the structure, which wasn't the ideal way I wanted to use.
I've got PostgreSQL 8.0.4 running on SuSE 9.3.

Regards,
Shiming