Heiko,

>See my other posting: I found out about another gds_lock_mgr instance
>running on the server. Started by the InterClient server.

Ah... OK. That would produce exactly the results you're seeing.
The InterClient server is looking for libgds.so. Firebird 1.5
dropped the 'gds' and went to firebird libraries. Get rid of the
/opt/interbase completely and create a link with that name to
the firebird client library.

Regards,

Ann