I have tried different linux distros, different versions of postgresql and have even found a freebsd user with the same error. I can't get
a regular database owner in postgresql to work with otrs it has to be superuser some reason. That is not good security wise. Once I give super user to config.pm database user it works.

I found a freebsd user with the same error message:
freebsd same error message on root@localhost login: http://groups.google.com/group/lucky.freebsd.ports.bugs/browse_thread/thread/de34eaeecfa98a24?pli=1

syslog errors I get:

Sep 19 15:38:26 help OTRS-CGI-10[6480]: [Error][Kernel::System::Valid::ValidIDsGet][Line:120]: ERROR: permission denied for relation valid , SQL: 'SELECT id FROM valid WHERE name = 'valid''
Sep 19 15:38:26 help OTRS-CGI-10[6480]: [Error][Kernel::System::Auth::DB::Auth][Line:96]: ERROR: syntax error at or near ")" at character 51 , SQL: 'SELECT pw, id FROM users WHERE valid_id IN ( ) AND login = 'root@localhost''
Sep 19 15:38:26 help OTRS-CGI-10[6480]: [Notice][Kernel::System::Auth::DB::Auth] User: root@localhost doesn't exist or is invalid!!! (REMOTE_ADDR: 10.254.7.157)

It has somethingto do with using postgresql if is use mysql it works like a charm.

Anyone have any pointers.