I think i found the problem!
The code generated for the login form calls the function "ValidatedField" but the "webassist/security_assist/helper_php.php" does not contain this function. This function is contained in "webassist/form_validations/wavt_validatedform_php.php".
If i include this file as required in the login.php then the form works.
WA why is the helper file that includes the used function not included when creating the SA pages?