Can't POST FormData from iBooks widget on iPad

Question

I have a Dashcode widget that simply submits contact information from a three-field form to a PHP script on our server. It works properly when run/debugged from Dashcode. But when I drop it into iBooks Author and preview it on an iPad (either v2 or v3), the XMLHttpRequest POST no longer works properly. On the server, the form is ocassionally received with a request type of "OPTIONS" instead of "POST" so none of the form data is available to the server-side script. The content length is also reported as 0 (zero) on the server. Other times, the data is received correctly, but the widget's onerror function fires instead of onload, even when a 200 status is returned from the server.
The code worked fine in both Dashcode and on the iPad in a test iBook. Then I tested it after disabling wifi to ensure that errors would be handled properly. It hasn't worked again since enabling wifi. It could be a coincidence. I've relaunched iBooks, deleted and reinstalled the book, restarted the iPad, restarted Dashcode and iBooks Author. I've even created a new widget with nothing but a Submit button and hard-coded form values:
function submit(event)
    var formData = new FormData();
    formData.append("name", 'Name');
    formData.append("email", 'Email');
    formData.append("question", 'Question');
    var xhr = new XMLHttpRequest();
    xhr.open("POST", "http://www.example.com/example.php");
    xhr.onload = function(e) {
        if (this.readyState == 4) {
            if (this.status == 200) {
                helloText.innerText = 'Success';
    xhr.onerror = function(e) {
        helloText.innerText = 'Error: ' + this.status + ': ' + this.responseText;
    xhr.send(formData);
The widget is set to Allow Network Access and "10.4.0 (backward-compatible)". Any tips will be greatly appreciated.

Answer 1

I tried saving the .ibooks file and sync'ing it through iTunes instead of using Preview, but see the same result. The post data was received successfully on the server. Although the server sends a 200 status code, the widget's onerror function fires and reports a status of "0" and empty responseText.
This is a step in the right direction. But we can't use it if we can't properly provide success/failure feedback to the user.