[solved] error after backup and restore

Hello, I did a backup of a site in one vps and restored in another vps. When I clicked on "Edit Users" link in virtualmin for a virtual server, I get this error.

SQL select user.user,user.password from user,db where db.user = user.user and (db.db = '*****' or db.db = '*****') failed : Webmin cannot parse the output from the mysql command due to the nature of data in your database. You will need to install the DBI and DBD::mysql Perl modules to solve this problem.

I am able to view users of other virtual servers by clicking "edit users".

when I click on "MySQL Database Server" in webmin -> servers,

I am also not able to delete this virtual server.

When I try to compose a mail in postfix, the error appears again.

I tried to change administrative username and this error appears again.

I checked in webmin -> perl modules -> existing modules and the two modules are already installed.

DBD::Pg     1   PostgreSQL database driver for the DBI module   2.15.1-4.el6_3  07/Aug/2009 10:25
DBI     44  Database independent interface for Perl     1.609-4.el6     19/Aug/2010 20:33

( I have full root access to my server. )

Please suggest. Thanks