current_user changes immediately after login

[Christian Schröder <cs(at)deriva(dot)de>]

Hi list,
I have a strange problem: When I connect to one of my databases, the 
current_user immediatly changes without any interaction from my side. 
This is what I do:

chschroe(at)db1:~> psql -h db2 testdb
Welcome to psql 8.2.5, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
      \h for help with SQL commands
      \? for help with psql commands
      \g or terminate with semicolon to execute query
      \q to quit

testdb=> select session_user;
session_user
--------------
chschroe
(1 row)

testdb=> select current_user;
current_user
--------------
itstaff
(1 row)

How can this happen? The consequence of this is that I cannot access the 
tables because the role "itstaff" has no privileges. "reset role" does 
not have any effect. After "set role none" the current_user is equal to 
the session_user and the tables are accessible again.

This problem does only occur with this database. Do you have any 
explanation?

Regards,
   Christian

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