It looks like the extensions didn't install correctly. Please try completely removing the extensions with the extension manager and reinstalling them. This error shouldn't occur in the latest versions.
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.