please provide some additional details.
What is your OS?
What version Of Dreamweaver are you using?
What extensions are installed in the extension manager, including the version numbers?
if you are running DW CC or above, do you have the deprecated server behaviors extension installed?
http://www.webassist.com/tutorials/Deprecated-Server-Behaviors-for-Dreamweaver-Creative-Cloud
Before running the security assist wizard, do you have a Database connection created?
http://www.webassist.com/tutorials/Create-a-PHP-database-connection
Do you have a site properly defined?
http://www.webassist.com/tutorials/Define-a-dynamic-site-in-CS5