> Just after posting the question, i found an old thread about this issue.
>
> It seems the problem is in the firebird client library and i need to
> create a new connection, transaction and query inside the thread.
>
> Is it still valid for FB 2.0.3?

Yes. Beside the fact, that a thread should be seen as an isolated
entity, e.g. as data module, you also must use a TCP/IP connection, even
if it is a local connection.

There is also an IBO example about threads in your IBO distribution
here: %IBO%\Samples\Threads


HTH

--
Best Regards,
Thomas Steinmaurer
LogManager Series - Logging/Auditing Suites supporting
InterBase, Firebird, Advantage Database, MS SQL Server and
NexusDB V2
Upscene Productions
http://www.upscene.com