Hi,

When we sometimes (not all the time) save an XForm of a page in the CMS we get the following error:

Exception information:
Exception type: HttpException
Exception message: 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.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Page.LoadAllState()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Request information:
Request URL: https://www.XXXX.com:443/cm/ui/cms/edit/editpanel.aspx?id=143952&epslanguage=cy-GB
Request path: /cm/ui/cms/edit/editpanel.aspx
User host address: 162.158.158.124
User: helena.scott
Is authenticated: True
Authentication Type: Forms
Thread account name: NT AUTHORITY\NETWORK SERVICE

Thread information:
Thread ID: 15
Thread account name: NT AUTHORITY\NETWORK SERVICE
Is impersonating: False
Stack trace: at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState)
at System.Web.UI.Control.LoadViewStateRecursive(Object savedState)
at System.Web.UI.Page.LoadAllState()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Do you know why this maybe?

Thanks