[Samba] losing machine a/c and user password

[mallapadi niranjan]

Hi all

I have been using samba 3.0.21 with openldap , and facing some problems. i
have taken backup of the ldap daily in ldif file.
unfortunately our UPS got down and my PDC got rebooted, as a result my ldap
database got corrupted i believe,
using ldif file with slapcat command, i restored the ldap database, but my
windows clients had to rejoin again and
all my user's passwords had to resetted. why is this happening, how can i
preven this,

Regards
Niranjan