when I use Gbak I have the folowing :

J:\Program Files\Firebird\bin>gbak -b -l -user agde -password cmo -v -
z e:\ib\agde.gdb e:\ib\test.gbk
gbak: gbak version WI-T6.2.679 Firebird Release Candidate 2
gbak: Version(s) for database "e:\ib\agde.gdb"
Firebird/x86/Windows NT (access method), version "WI-T6.2.679
Firebird Release Candidate 2"
on disk structure version 10.0
gbak: readied database e:\ib\agde.gdb for backup
gbak: creating file e:\ib\test.gbk
gbak: starting transaction
gbak: ERROR: invalid transaction handle (expecting explicit
transaction start)

What is that error ?