>>> With embedded firebird I did run into an Access-Violation when my
>>> VB6-Application is terminated, there Seems to be an thread left over
>>> after disconnection all databases.
>>
>> What FB version do you use ?
>
> It is 2.1.3
>
>>> Is there an Option to shut down embedded engine completely?
>>
>> Only in Firebird 2.5.
>
> What is to do in 2.1.3?

At first, produce crash dump and make it available for analisys.
And, of course, ensure you really have all attachments closed when
application is terminated.

Regards,
Vlad