?invalid=true means that the server validation is failing, the email won't get set if validation fails.
to determine which validation is failing edit:
PostResult($WAFV_Redirect,$WAFV_Errors,"contactus");
to:
die($WAFV_Errors);
PostResult($WAFV_Redirect,$WAFV_Errors,"contactus");
this will show a comma separated list of numbers indicating the failed validations. using that I can tell which validation is failing.