Padding is invalid and cannot be removed

I occasionally get the following exception from an ASP.NET 2.0 Web Application running on a web host .I am using flex and fluorinFx I have everything running perfectly on my local machine; however, when I deploy to the test servers, After some remote call, I just get this message and nothing to work until clear the cache Can anyone help me?? The error message is : Endpoints.Filter.AuthenticationFilter - Padding is invalid and cannot be removed. System.Security.Cryptography.CryptographicException: Padding is invalid and cannot be removed. at System.Security.Cryptography.RijndaelManagedTransform.DecryptData(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount, Byte[]& outputBuffer, Int32 outputOffset, PaddingMode paddingMode, Boolean fLast) at System.Security.Cryptography.RijndaelManagedTransform.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount) at System.Security.Cryptography.CryptoStream.FlushFinalBlock()
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