>
> You need exclusive access to make these changes. You must have an open
> transaction somewhere.
>
> Adam
>

Great, Adam,
my open ISQL session was the problem! It was the 'open transaction'. I
closed it and continued working.
I got the problem:
it was a row in table DR that had the foreign key that held a value,
say 5, that did not exist in table DT as a key.
You may wonder why this could happen... well, it's not so uncommon !
Don't know if it is my app or FB1.0 (btw this DB has forced writes =
OFF :( ) ,
but I did the following:
- removed the 'wrong' row in table DR,
- double checked its removal,
- gbak'd the DB,
- restored the DB --> restore OK.
Thanks, Adam!
Luca.