Eric,

Those symptoms are quite unusual.

I repeated your test here

connect "localhost:C:\Program
Files\Firebird\Firebird_1_5\examples\EMPLOYEE.FDB" user sysdba
password masterkey;

select coalesce(job_code, 'blah') from job;

COALESCE
========

CEO
CFO
VP
Dir
Mngr
Mngr
Admin
Admin
Admin
PRel
Mktg
Mktg
Accnt
Finan
Eng
Eng
Eng
Eng
Eng
Eng

COALESCE
========
Doc
Doc
Sales
Sales
SRep
SRep
SRep
SRep
SRep
SRep
SRep

Well there are no nulls to speak of in the data, but the function
clearly worked.

Alexandre might be on to something. Coalesce is a new feature in 1.5.
so if you are using the embedded dll, when you make a connection to a
hostname:path, it just acts like a normal client, but that should give
you a few ideas anyway.

Adam