Asynchronous calls issues in Drupal using inline entity?

Question

I am getting the following error:

Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check http://xhr.spec.whatwg.org/.

I have a content type called "resource" and on it you can create "inline entity nodes" which is basically just new nodes linked to this node. My problem is that when I add a new node and then try to upload a file, it reloads the page and gives this error.

This does not happen on the normal upload. There it would also reload the page, but it would keep the image intact. I think the same happens with Inline entities except that inline entities dont save the state when an error like this happens.

That is why I think I need to find a way to STOP the error from being throw in the first place. I've narrowed it down to jquery.js?v=1.5.2 line 7268 (it's similar for most of the other versions)

send: function( headers, complete ) {

    // Get a new xhr
    var xhr = s.xhr(),
                handle,
                i;

    // Open the socket
    // Passing null username, generates a login popup on Opera (#2865)
    if ( s.username ) {
        xhr.open( s.type, s.url, s.async, s.username, s.password );
    } else {
        xhr.open( s.type, s.url, s.async );
    }
....

This error doesn't happen on my local machine and I have ssl running on the web server where this error is happening.

I have:

• Switched between different JQuery versions
• Considered that it might be in the file upload module, but that's part of core now.
• Considered upgrading the inline entity module, but it is definitely the latest version and I tried dev, but still no changes
• I upgraded to Drupal 7.37 (latest to date), still broken
• I ran updates, still nothing

So the question is, why is this error being thrown in Drupal and how can I fix it?

UPDATE

I actually went into the Jquery file and changed:

 xhr.open( s.type, s.url, s.async );

to:

 xhr.open( s.type, s.url, true );

Now it no longer throws the error, but it still doesn't show the image...