Hallo,
I have the same problem (Firebird RC1, W2000). I'l try to explain
it.
When I do backup for the first time, there is the following piece of
text in backup log:

gbak: writing privilege for user PUBLIC
gbak: writing generator RDB$SECURITY value 0
gbak: writing table constraints

When I do restore, there is the following piece of text in restore log:

gbak: restoring privilege for user PUBLIC
gbak: restoring generator RDB$SECURITY value: 0
gbak: creating indexes

Then there will be a new record in the table RDB$GENERATORS
(RDB$GENERATOR_NAME = RDB$SECURITY, RDB$SYSTEM_FLAG = null).
So when I do backup for the second time, this new generator is backuped

gbak: writing generator GEN_RADA value 172
gbak: writing generator RDB$SECURITY value 0
gbak: writing stored procedures

And when I do restore, generator RDB$SECURITY is restored and after
restoring privileges the following error is arised:

Error 335544349
Attempt to store duplicate value (visible to active transactions) in
unique index "RDB$INDEX_11"

because gbak attempts to store the second generator RDB$SECURITY into
the table RDB$GENERATORS.

Regards
Petr Hartman

----- Original Message -----
From: "Claudio Valderrama C." <cvalde@...>
> I managed to clean your script from strange characters when taken from
the
> newsgroups. Ran it. Connected to the db. Backed up it. Restored it.
Sent in
> both cases the output to files. No problem. Sorry, can't reproduce the
bug.
> After the privileges were restored, gbak created the indices and
finished.
>
> "Raf Schandevyl" <Raf.Schandevyl@...> wrote in message
> > This is the error I'm getting.
> >
> > gbak: restoring privilege for user SYSDBA
> > gbak: ERROR: attempt to store duplicate value (visible to active=20
> > transactions) i
> > n unique index "RDB$INDEX_11"
> > gbak: Exiting before completion due to errors