Well Jan, the only unusual thing I see with your current SQL statement is
your excessive use of brackets, but that shouldn't cause any problems.

But in your original statement you said "this worked with IBO3 but started
to generate the error after upgrading to IBO4 and firebird 1.0", which
makes me wonder if it can have something to do with you upgrading to
Firebird 1.0. If you create tables using doublequotes around the
identifiers, these identifiers become case sensitive in Firebird and can
only be accessed using doublequotes. Try to recreate your table without
using any doublequotes and see if your statement will work then.

If this doesn't work, I'm about to run out of ideas.

HTH,
Set