Hello,
I have this problem. With a script i change the db structure of 12 DB's.
It works korrect with 4 db's. And then this:

Unsuccessful execution caused by a system error that precludes
successful execution of subsequent statements.
internal gds software consistency check (cannot find record fragment
(248)).

And this was the deathblow for the DB 5. Oh, i'm so happy, that i have
a backup :-).
This was the second fall in two days.

Server version: WI-V6.3.4.4910 Firebird 1.5
SQLDialect: 1. ODS: 10.1. Forced writes: Off. Sweep inteval: 20000.
Page size: 4096. Cache pages: 2048 (8192 Kb). Read-only: False.

The scripttool is ibexpert.

Frank