Hello, Bogdan!

>We are planning to upgrade to Firebird-1.0.3.972 soon
>still i would like to know why such things continue to happen

As I can see, you have the single error - index is corrupted and one of its
b-tree pages is confused.

Did you perform the gfix/gbak operations to repair your database every time
you see such error?

To know more about corruptions, see these links
Diagnosing and Repairing InterBase Database Corruption
http://ibphoenix.com/main.nfs?a=ibphoenix&l=;IBPHOENIX.PAGES;NAME='ibp_db_co
rr'

Known Causes of Corruption in InterBase Databases
http://delphi.weblogs.com/stories/storyReader$232

Recovery guide "How to recover InterBase/Firebird database"
http://www.ibsurgeon.com/guide.html

Also you can check your database with IBFirstAID Diagnostician for physical
errors.

Sincerely yours,
Alexey Kovjazin
www.ib-aid.com