Please undo all changes that you made in the file mysql.lib.php. Make sure that the file is exactly as it was before! If you want that we are able help you, dont do any hectic changes in the sources of ispconfig as thats not required and you will mess up our setup more and more by doing that.
Your problem is that you changed the mysql root password without changing it in the file /usr/local/ispconfig/server/lib/mysql_clientdb.conf. So edit only this one file and set the new root password there.