>> If it turns out that your Firebird 1.5 CS does not support backup via
>> services
> It does via gbak but not via the JDBC driver

You mean, that gbak from FB 2.0 can use Services API to do the job?
Hmmm... then this is some kind of a bug in Jaybird.

Can you install packet capturing software (e.g. Ethereal) on your client
and dump the communication between Jaybird and FB 1.5 CS and then
between gbak with -se switch and FB 1.5 CS?

Roman