security assist V2 is not supported under Dreamweaver CS3.
the following are the system requirements for Security Assist 2:
Windows
Windows 7, Windows Vista, Windows XP SP2
Dreamweaver CS5, Dreamweaver CS4
Macintosh
Mac PowerPC or Mac Intel
MacOS 10.4.x or greater
Dreamweaver CS5, Dreamweaver CS4
Application Server Model and Database
PHP 5.2 +
MySQL 5