I purged my existing mysql-server from ubuntu and re-installed the same. This was due there was an upgrade from my ubuntu and I was unable to start my sql-server.

After cleaned up and taking backup of my data , I re-insalled mysql.

During installaion I received following message popup.

Unable to set password for the MySQL "root" user      
An error occurred while setting the password for the MySQL administrative user. 
This may have happened because the account already has a password, or   because of a communication problem with the MySQL server. 
You should check the account's password after the package installation.      
Please read the /usr/share/doc/mysql-server-5.5/README.Debian file for more
information.                                                                ¦    
                                                        ¦    

After the installation was failed, following error were received.

        121109 20:36:18 InnoDB: Initializing buffer pool, size = 128.0M
        121109 20:36:18 InnoDB: Completed initialization of buffer pool
        121109 20:36:18 InnoDB: highest supported file format is Barracuda.
        121109 20:36:18  InnoDB: Waiting for the background threads to start
        121109 20:36:19 InnoDB: 1.1.8 started; log sequence number 2395841
        ERROR: 130  Incorrect file format 'user'
        121109 20:36:19 [ERROR] Aborting

    121109 20:36:19  InnoDB: Starting shutdown...
    121109 20:36:20  InnoDB: Shutdown completed; log sequence number 2395841
    121109 20:36:20 [Note] /usr/sbin/mysqld: Shutdown complete

    start: Job failed to start
    invoke-rc.d: initscript mysql, action "start" failed.
    dpkg: error processing mysql-server-5.5 (--configure):
     subprocess installed post-installation script returned error exit status 1
    dpkg: dependency problems prevent configuration of mysql-server:
     mysql-server depends on mysql-server-5.5; however:
      Package mysql-server-5.5 is not configured yet.
    dpkg: error processing mysql-server (--configure):
     dependency problems - leaving unconfigured
    No apport report written because the error message indicates its a followup error from a previous failure.                                                                                                        Errors were encountered while processing:
     mysql-server-5.5
     mysql-server
    E: Sub-process /usr/bin/dpkg returned an error code (1)