Invalid length for a Base64 char array

Error message: Invalid length for a Base-64 char array.
--------------------------------------------------------------------------------------

Error source:mscorlib
Stack message:   at System.Convert.FromBase64String(String s)
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
   at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState)
   at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)
   at System.Web.UI.HiddenFieldPageStatePersister.Load()
--------------------------------------------------------------------------------------

服务器换到IIS7  并且让32bit生效后出现这个问题