AjaxFileUpload displaying Red error after Upload button clicked

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C#

VS2010

HTML5

Hi,

I am having problem with the AjaxFileUpload that enables dragging and dropping of images. Upon clicking "Upload" the file does not upload and shows a red "error" message by the side of the file.

Would greatly appreciate, if someone can provide the solution to it.
Below is a snippet of my code.

.aspx page

<ajaxToolkit:AjaxFileUpload
        id="ajaxUpload1"
         önUploadComplete="ajaxUpload1_OnUploadComplete"
        ThrobberID="MyThrobber"
        MaximumNumberOfFiles="1"
        AllowedFileTypes="jpg,jpeg,gif,png"
         runat="server"  />

        <asp:Image
            id="MyThrobber"
            ImageUrl="~/images/ajax-loader.gif"
            Style="display:None"
            runat="server" />

.cs

protected void ajaxUpload1_OnUploadComplete(object sender, AjaxControlToolkit.AjaxFileUploadEventArgs e)
{
    // Generate file path
    string filePath = "~/images/" + e.FileName;

    // Save upload file to the file system
    ajaxUpload1.SaveAs(MapPath(filePath));
}