I reset the workspace and deleted the cache file and I got the same error. The info you requested is listed below.
What is your OS? OS X 10.9.1
What Version Of Dreamweaver? CS4 and CS5, but eCart has always worked better in CS4
What Version of eCart? eCart 4.5.2
What other extension including the version numbers are installed? DataAssist 2.1.0, Universal Email 4.0.1, SecurityAssist 1.1.9, Form Toolkit 1.0.0 and Cookies Toolkit 3.1.2