> Are you telling us that you simply switched your live production system over from Fb 1.5.5 to Fb 2.1.2 without any mind to the changes in two full releases? Whatever else you do, don't delete your last good backup.

I'm not telling that at all.
We made enought copies...

Our migration process is based on "CloneDatabase" procedure :
1- Extract metadata
2- Create target database
2- Copy data
3- Compare data
All steps were OK.

I confirm that backup/restore solved index problem.

Nothing else has changed on this server but firebird 1.55 to 2.12 upgrade. So I think that antivirus and gdb are not problems in this case.

Is there any way to know moore about fbserver executing context when occurs such error ?

thanks