> We use FBManagedConnectionFactory.

Hmm... According to the specs, Connection.setTransactionIsolation(...)
may (or maybe even should) commit current transaction when isolation
level is changed. When you use FBManagedConnectionFactory, you're
working in managed environment and transaction management is not
allowed in the client code. I am not JCA expert, but I suspect that
you should not call setAutoCommit(), setTransactionIsolation(),
commit() and rollback() when using driver in JCA mode.

I'm not sure if this is a bug or deviation from the specification, but
I will check.

> Another problem we found during our work was problem with Long fileds
> in FB.
>
> there was exception about atrying to access null object in getLong I
> think.

Do you have a stack trace?

Thanks!
Roman