Checkbox not visible on nodes of TreeView control when deployed in IIS

Not an answer yet, needed to show the images, well I tried the same, used this code in aspx: (I did not change any setting in IIS, nothing in aspx as well, created a plain solution >> added the treeview and deployed.)

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server"> 
    <div> 
        <asp:TreeView ID="TreeTest"
            EnableClientScript="true"
            PopulateNodesFromClient="true"
            ExpandDepth="0"
            ShowLines="true"
            ShowExpandCollapse="true"
            ShowCheckBoxes="Root"
            OnTreeNodePopulate="TreeTest_TreeNodePopulate"
            Width="1px"
            runat="server"> 
            <Nodes>
                <asp:TreeNode Text="Something">
                    <asp:TreeNode Text="11"></asp:TreeNode>
                </asp:TreeNode>
                <asp:TreeNode Text="Something">
                     <asp:TreeNode Text="11"></asp:TreeNode>
                </asp:TreeNode>
                <asp:TreeNode Text="Something"></asp:TreeNode>
            </Nodes> 
        </asp:TreeView>  
    </div>
</asp:Content>

Checked in my local could see this:

Deployed in IIS version 6.2 , windows server 2012, could see this:

There must be something else which is preventing the checkboxes in your page. Show more code.