This is an error that is being caused as a result of a conflict with Security Assist. we are currently working on a solution for this error.
in the mean time, you can disable Security Assist in the extension manager to work around the error.
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.