The System Requirements should not have shown CS3 support when security assist was released. We have not done any testing of Security Assist in Dreamweaver CS3.
when we release new versions of software, our policy is to support the current version of Dreamweaver and on version back.
All of the support tickets that have been created for CS3 issues where to address installation, but we cannot offer further support than that in Dreamweaver CS3.
If you would like to request a refund, please contact our sales depart by email at sales AT webassist DOT com