The click event of the toolbar is triggered only when the user clicks outside of the set button icon (the text or the button element). Clicking directly over the icon does not perform any action in IE11.

video: https://www.screencast.com/t/K50K4X8Ck

Code to reproduce:
            <telerik:RadToolBar runat="server" ID="ToolBar1">
                <Items>
                    <telerik:RadToolBarButton
                        ImageUrl="//d585tldpucybw.cloudfront.net/sfimages/default-source/labs/kendo/kendoka-states.png"
                        NavigateUrl="Default.aspx"
                        Text="Link"/>
                    <telerik:RadToolBarButton
                        ImageUrl="//d585tldpucybw.cloudfront.net/sfimages/default-source/labs/kendo/kendoka-states.png"
                        NavigateUrl="Default.aspx"/>
                </Items>
            </telerik:RadToolBar>

 <telerik:RadToolBar ID="toolbarRibbon" runat="server" Orientation="Horizontal" Width="100%" RenderMode="Lightweight"

           OnClientButtonClicking="OnClientButtonClicking"
          OnClientButtonClicked="OnClientButtonClicked">
        <Items>
            <telerik:RadToolBarButton ID="toolBtnAnalyses" runat="server"
                Text="Analyses"
                Visible="true" Target="_blank"
                NavigateUrl="About.aspx" 
                ImagePosition="AboveText" CheckOnClick="true" ImageUrl="Content/chart.png" />
              <telerik:RadToolBarButton ID="RadToolBarButton1" runat="server"
                Text="Analyses"
                Visible="true" 
                NavigateUrl="About.aspx" 
                ImagePosition="AboveText" CheckOnClick="true" ImageUrl="Content/chart.png" />
        </Items>
    </telerik:RadToolBar>

There is a workaround if the button's ImagePosition is set to "Left" or "Right":

.rtbImage {
    pointer-events: none;
}