For the initial error, have you tried Deleting the Dreamweaver Cache file from the users configuration folder:
common_installation_issues.php
if you continue to get the error, edit your site definition, and make sure that in the testing server settings, you have set the application modal to PHP.
for the error in the browser, make sure that you have uploaded the webassist/form_validations/wavt_scripts_php.php file to the server.