>What you use to develop programs ? IBX ?

No, he does not. Originally Lester used the BDE and tried for a long time
to make it work. Then he switched to IBO and things started working...

I've read that IBX has improved considerably the last few years, but it
does not support Firebird other than by accident and as new features are
added it will become less and less appropriate for Firebird.

>Please say to me: what is ambiguous query ?
>I read about it, but I'm not sure.

SELECT FIELDA
FROM A JOIN B ON B.FIELDA=A.FIELDA

is ambiguous because it does not specify whether FIELDA should be taken
from table A or B. Actually, this is the one case where it is not really
ambiguous since you join on that very field and know it has the same value
in both A and B, but Firebird nevertheless complains.

There is another thing that can cause you problems - use of new reserved
words as field names. E.g. if you have a field named FIRST, it will have to
be renamed.

By the way, we also switched from IB 5.6 to FB 0.9.4 and have not had any
problems with that. Currently we use Fb 1.0.2 and will await Fb 1.5 until
it is released for production.

HTH,
Set