ArcGIS Server 9.3.1
Custom Web ADF App
MS Server 2003

Getting a TOC 'Index out of range' error in server's Event Viewer when user interacts with the map after session times out.

Steps:
1. Let app time out.
2. Click any AJAX enabled control other than map.
3. Zoom or pan the map.
4. Error.

If I skip step 2 above and do not cause any callbacks before mousing the map, the ESRI.ADF.System.showLapseAlert Javascript fires successfully and I can refresh the page with no problem. However, If I do cause any callbacks before mousing the map, the ESRI.ADF.System.showLapseAlert Javascript still fires successfully, but when I refresh the page, I get an error, part of which is shown below:

Thread Information:
Thread ID: 4
Thread account name: myServer\Administrator
Is impersonating: False
Stack trace: at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
at System.ThrowHelper.ThrowArgumentOutOfRangeException()
at System.Collections.Generic.List`1.get_Item(Int32 index)
at ESRI.ArcGIS.ADF.Web.UI.WebControls.Toc.checkLayerVisibilityAndEnsureMime(TreeViewPlusNode node, Double newScale, Boolean ensureMime)
at ESRI.ArcGIS.ADF.Web.UI.WebControls.Toc.doScaleDependentVisibilityAndEnsureMime(Double newScale, TreeViewPlusNodeCollection nodes, Boolean ensureMime)
at ESRI.ArcGIS.ADF.Web.UI.WebControls.Toc.PopulateTreeNodes(List`1 hiddenLayers, String separator)
at ESRI.ArcGIS.ADF.Web.UI.WebControls.Toc.OnPreRender(EventArgs e)
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Control.PreRenderRecursiveInternal()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

This does not occur with the out-of-the-box web mapping application so it must be something I am missing in my code.

Thanks in advance for your help in solving this problem.

-Dan