Recreate the users configuration folder, step 12 of the adobe troubleshooting guide:
http://helpx.adobe.com/dreamweaver/kb/troubleshoot-javascript-errors-dreamweaver-cs4.html#main_user_config
then reinstall the extensions using the following order:
eCart 5.0.7
Free Tools 1.0.5
Design Extender 1.1.5
Data Bridge 1.1.4