Why the QWebView does not execute the script on this webpage?

Here is the code from the MainWindow constructor:

Code:

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view = new QWebView(this);
view->load(QUrl("http://checkusernames.com/"));

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The page loads fine and there is a script on that page which is supposed to be executed when the "Check User Name" button is clicked (manually). It executes fine in IE and FireFox, but in the QWebView nothing happens. My question is: Why this script is not executed in the QWebView?
I have the WebAttribute JavascriptEnabled set to true...

So it doesn't work if you click on the button, yes?

yes, when you click on the button nothing happens.

It doesn't mean the script didn't execute. Fire up the web inspector and check there, maybe you'll get some more info.

I did activated the web inspector, but I'm not sure I have enough knowledge to determine where the problem might be. :(
I see one script error:
TypeError: 'null' is not an object (evaluating 'b.each') - cloudflare.min.js:22
but it does not seam to be related to the script that is supposed to be executed when the button is clicked.
I would really appreciate some more help on this.