Failed to load viewstate

[kalia]

Hi All,

We are getting a "Failed to load viewstate" error occasionally.

The exact error is as follows:

Failed to load viewstate. The control tree into which viewstate is being
loaded must match the control tree that was used to save viewstate during
the previous request. For example, when adding controls dynamically, the
controls added during a post-back must match the type and position of the
controls added during the initial request.
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.AddedControl(Control control, Int32 index)
at System.Web.UI.ControlCollection.Add(Control child)
at OC_WebControls.TocControlContainer.CreateControls(ResourceManager
LocRM, WebControlFactory ControlFactory, DataRow[] Rows, Hashtable
htParentControls)
at Jupiter.RunTimeForm.ConstructFormView(DataSet dsScreenDefinition)
at Jupiter.RunTimeForm.Page_Load(Object sender, EventArgs e)
at System.Web.UI.Control.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain()

There are many controls on the form, mostly dot net controls including
textboxes, labelse, checkboxes, htmlimage, hidden field, combo, etc...but
also UltraWebGrig and UltraWebTab from Infragistics.

The problem is diffiult to reproduce using the debug version of the
application so we havn't pin pointed which control has the problem. (I will
put in a try...catch which throws an error idenitifying the control name and
test a 'Release' version.)

The problem arrises after the site has been used for some time, then
frequently occurrs, then disappears for a long time, only to reappear later.

We are using .Net Framework version 1.1.4322

Any assistance you can provide is appreciated.
Regards,
Eamon.