Site Asisst 3 is not compatible with Dreamweaver CS5. It is compatible with Dreamweaver 8, CS3.
You will need to upgrade to Site Sculptor for CS5 compatibility.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.