> In org.firebirdsql.ngds.isc_db_handle_impl debugger is stoped on the
> line with asterisks
> (87) public int getRdb_id() {
> (88) checkValidity();
> (89)*** return rdb_id;
> (90) }

This is completely strange - it should not hang in "return" clause...

> No exceptions thrown (well there is one since first jaybird is
> trying to load .dll and than .so file but this is irrelevant)
> Now when I continue, application is supposed to go back to
> org.firebirdsql.ngds.GDS_Impl method isc_attach_database
> ...
> But it stops....

Also strange... Are you able to test somehow whether embedded server works
at all in your setup. You can try for example writing small application that
uses DriverManager to obtain connections (no pools).

> I read FAQ supplied with jaybird, but I found information how to
> disable logging, not how to enable it.

See http://jaybirdwiki.firebirdsql.org/FAQ/JayBirdLogging

> Can this information help to track down the problem?

Can you prepare a small test case, I will try it in my setup (Debian Linux,
JayBird 1.5 release + Firebird 1.5.x embedded).

Roman