Urgent Help needed with viewstate

[Guest]

we have web application up running in real environment now, after view did
deployment a problem appeared caused by ViewState an exceptions like the
following are generated:

Message:
Invalid length for a Base-64 char array.
Trace:
at System.Convert.FromBase64String(String s) at
System.Web.UI.LosFormatter.Deserialize(String input) at
System.Web.UI.Page.LoadPageStateFromPersistenceMedium()



Message:
Unable to validate data.
Trace:
at System.Web.Configuration.MachineKey.GetDecodedData(Byte[] buf, Byte[]
modifier, Int32 start, Int32 length, Int32& dataLength) at
System.Web.UI.LosFormatter.Deserialize(String input)


this problem appeared on in one page which has 16 user controls and uses the
same ViewState Names ( we have 19 main viewstates) .

what should I do in this case?