Treepanel beforeload event problem

[Mr.Techno]

Hi friends,
i am using treepanel, i am facing problem in beforeload listener...sometimes it working fine...sometimes the method is not at all calling..(i observed this behaviour when i clicked four or five nodes one after another)can u tell me what could be the problem.. Below is the code of my treepanel

<ext:ResourceManager ID="ResourceManager1" runat="server" />
        <ext:TreePanel ID="TreePanel1" runat="server" Title="Tree" AutoHeight="true" Border="false"
            RootVisible="false" SingleExpand="true" TrackMouseOver="true" Icon="ChartOrganisation">
            <Root>
                <ext:AsyncTreeNode NodeID="0" Text="Root" />
            </Root>
            <Listeners>
                <BeforeLoad Fn="nodeLoad" />
                <Click Fn="nodeSelected" />
            </Listeners>
            <SelectionModel>
            <ext:DefaultSelectionModel runat="server" />
            </SelectionModel>
        </ext:TreePanel>

below are the javascript functions

<script type="text/javascript">
     function nodeLoad(node) {
         Ext.net.DirectMethods.NodeLoad(node.id, {
             success: function(result) {
                 var data = eval("(" + result + ")");
                 node.loadNodes(data);
             },

             failure: function(errorMsg) {
                 Ext.Msg.alert('Failure', errorMsg);
             }
         });
     }
 
        function nodeSelected(node) {
            //alert(node.parentNode.id+':'+node.id);
            Ext.net.DirectMethods.GetT2Metrics(node.parentNode.id, node.id);
        }
    </script>

I am using IE9, VS2008, Ext.Net 1.0
please help me ..why beforeload event is not firing sometimes...

[Mr.Techno]

please....can anybody tell me what is the problem....

how to solve this issue?