asp.net - IE 11 multiple postbacks issue

Since the coming of IE 11, we had troubles with our ASP website.

After a lot of research, we reduced the code to a very minimum to reproduce the error. At this point there are just two lines of code that still manage to crash the website. 

The problem that occurs is that when clicking the button multiple times in a row, the website will keep loading and will simply not work anymore. You need to click fast for about ten times before it crashes. On our live website however, which is a lot more complex, the issue sometimes already occurs on two clicks.

To reproduce the issue, place a button and label in a new website project, and c/p this code:

    Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        lblMenu.Text = "abcdefghijklmnopqrstuvwxyz abcdefghijklmnopqrstuvwxyz abcdefghijklmnopqrstuvwxyz abcdefghijklmnopqrstuvwxyz"
        System.Threading.Thread.Sleep(1000)
    End Sub

The code behind this website is pretty simple:

 1. I set the text of the label to something rather long
 2. Then I put the thread to sleep for 1000 ms. This mimics the loading effect which would occur on the actual website, eg. data being collected from the database.

Again, the problem only shows up in IE 11. It does not seem to happen in other browsers. 

Additionally, when the application Fiddler is active at the time you click multiple times in IE 11, the problem does not occur. The problem also does not occur when in debug mode (testing from Visual Studio).

I am using .NET framework 4.5. The website is currently hosted on a Windows 2007 server with Service Pack 2. 


Thanks