Good day -
It is common that if you do not know the MySQL Root that you likely do not know what the MySQL "Admin" account password that was created during the initial install either. That is the account the NSM application uses when it accesses the DB. After recovering the MySQL "root" password you would want to ensure that you also reset the MySQL-Admin account if you do not know what it is.
Instructions for that are in: http://kc.mcafee.com/corporate/index?page=content&id=KB53391
This is also the account credentials that you are prompted for when you run certain operations in the DBADMIN utility -- so is important to know.