> We deploy our solution using an application on server run from client.
> Some client, after update server to 2.1.1, give back this error after
> connection to database:
>
> SQL Error: Dynamic SQL Error SQL error code = -804 SQLDA missing or
> incorrect version, or incorrect number/type of variables.
>
> Some idea where investigate?

This error means that or application incorrectly fill SQLDA (parameters) or bug
in server (or in fbclient). There is one such bug fixed recently in HEAD (2.5 Beta1) :

http://tracker.firebirdsql.org/browse/CORE-2349

If error is reproducible try to use fbclient from FB 2.0.x and see if error is gone.
I.e. if you encountered CORE-2349, then it will be reproducible only with fbclient 2.1.x
and must gone with older fbclient.

Else you have to check your application code or, probably, create reproducible
test case for me to investigate.

Regards,
Vlad