strange problem with not existing roles

Hi list,
I have a strange problem in postgres (PostgreSQL 9.3.1, compiled by Visual C++ build 1600, 64-bit), there are granted
privilegeson schemas, tables, columns for roles that don't exist. 


Example:
In pgAdmin for schema user_data the follwing wrong grants are reported:
...
GRANT ALL ON SCHEMA user_data TO "482499";
GRANT ALL ON SCHEMA user_data TO "17708";
...


Problem is:
- these roles don't exist,
- they can't be dropped (DROP ROLE "482499"; => FEHLER:  Rolle „482499“ existiert
nicht)
- grants can't be revoked (REVOKE ALL ON SCHEMA "user_data" FROM "482499"; => FEHLER: 
Rolle„482499“ existiert nicht) 
- ROLES can be recreated and dropped afterwards, but the grants persists:
    CREATE ROLE "482499";
    DROP OWNED BY "482499";
    REVOKE CONNECT ON DATABASE "wver_ims" FROM "482499";
    REVOKE ALL ON SCHEMA "user_data" FROM "482499";
    DROP ROLE "482499";
- new tables can't be created in schemas with these grants
    CREATE TABLE user_data.test
    (
       id serial,
       PRIMARY KEY (id)
    );
    => FEHLER:  Rolle 17708 wurde gleichzeitig gelöscht
    
    
The roles are not listed in any catalog
    SELECT * FROM information_schema.xxxxxxx WHERE grantee in
('243683','243666','243689','482499','482499','17708');


Only in pg_auth_members there is a set for each of these roles:
    SELECT * FROM pg_catalog.pg_auth_members WHERE member in
('243683','243666','243689','482499','482499','17708');

 

What can I do to get rid of these roles and grants?

 

Ludwig