David,

yes, it seems that the db was corrupted.

I had to delete it and pump again data into it.

Coming to how:

>1. You were playing around with command line tools ;-)

no: I just learnt a little bit how to use gbak

>2. The W2000 machine crashed

no. I am amazed to see a MS product working 4 weeks w/o crashing :)

>3. You were using IBConsole or some other admin tool known to be
>seriously buggy

I mostly used WISQL and QuickDesk.

I played a lot with the db: deleting and re-creating constraints, fields
and whole tables, etc

But I always used SQL or the visual i/f of QuickDesk

>4. You were using different connect strings from Windows client
>machines.

no

>5. You were mixing remote and local access to the same database (I'm
>pretty sure that's a no-no, from what I've read, but I've never tried
>it myself ;-))

no

One thing comes to mind: sometimes I abruptly halted a transaction from
Delphi using CTRL-F2: could this corrupt the db ?

>Hopefully, it means you were using a test database that can be
>re-created from a script... :-)

happily this was - more or less - the case: the db was not yet in production

Thank you

Duilio