"Invalid length for a Base-64 char array" - A wierd problem

Hi Anyone,
I am getting following error message in my event log when users of my LIVE system using my application.
Message=Invalid length for a Base-64 char array.
SourceObjectName=mscorlib
StackTrace=   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()
The problem is that, it doesnt come at any fix place, and also I can't debug the code, as its on LIVE.
Can anyone please guide me which could be the possible reason of such problem?


Thanks

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