Error Specified key is not a valid size for this algorithm

Unexpected error: The specified key is not a valid size for this algorithm.
Parameter name: key
Details:
Microsoft.Mashup.Evaluator.Interface.ErrorException: The specified key is not a valid size for this algorithm.
Parameter name: key ---> System.ArgumentException: The specified key is not a valid size for this algorithm.
Parameter name: key ---> System.ArgumentException: The specified key is not a valid size for this algorithm.
Parameter name: key
at System.Security.Cryptography.AesCryptoServiceProvider.CreateEncryptor(Byte[] key, Byte[] iv)
at Microsoft.Mashup.EngineHost.Services.EncryptedPersistentCache.EncryptedStorage.EncryptPage(Byte[] input, Int32 count, Byte[] output)
at Microsoft.Mashup.EngineHost.Services.TransformingPagedStream.WritePage(Int32 page, Byte[] buffer, Int32 length)
at Microsoft.Mashup.EngineHost.Services.PagedStream.Flush()
at Microsoft.Mashup.EngineHost.Services.EncryptedPersistentCache.EncryptedStorage.CommitStream(Int32 id, Stream stream)
at Microsoft.Mashup.EngineHost.Services.WriteBehindPersistentCache.AsyncCommitStorage(String key, TemporaryStorage storage)
at Microsoft.Mashup.EngineHost.Services.WriteBehindPersistentCache.AsyncCommitStorage(Object obj)
at Microsoft.Mashup.Evaluator.EvaluatorThreadPool.EvaluatorThread(Object state)
at Microsoft.Mashup.Evaluator.SafeThread2.<>c__DisplayClass15.<CreateAction>b__14(Object o)
--- End of inner exception stack trace ---
at Microsoft.Mashup.Evaluator.EvaluationHost.<>c__DisplayClass7.<TryReportException>b__6()
at Microsoft.Mashup.Common.SafeExceptions.IgnoreSafeExceptions(IEngineHost host, IHostTrace trace, Action action)
at Microsoft.Mashup.Evaluator.EvaluationHost.TryReportException(IHostTrace trace, IEngineHost engineHost, IMessageChannel channel, Exception exception)
at Microsoft.Mashup.Evaluator.EvaluationHost.TryHandleException(Exception exception)
at Microsoft.Mashup.Evaluator.SafeThread2.HandleException(Exception e)
at Microsoft.Mashup.Evaluator.SafeThread2.<>c__DisplayClass15.<CreateAction>b__14(Object o)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart(Object obj)
--- End of inner exception stack trace ---
at Microsoft.Mashup.Evaluator.EvaluationHost.OnException(IEngineHost engineHost, IMessageChannel channel, ExceptionMessage message)
at Microsoft.Mashup.Evaluator.MessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.MessageHandlers.Dispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.ChannelMessenger.ChannelMessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.MessageHandlers.Dispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.ChannelMessenger.OnMessageWithUnknownChannel(IMessageChannel baseChannel, MessageWithUnknownChannel messageWithUnknownChannel)
at Microsoft.Mashup.Evaluator.MessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.ChannelMessenger.ChannelMessageHandlers.TryDispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.MessageHandlers.Dispatch(IMessageChannel channel, Message message)
at Microsoft.Mashup.Evaluator.Interface.IMessageChannelExtensions.WaitFor[T](IMessageChannel channel)
at Microsoft.Mashup.Evaluator.RemotePreviewValueSource.PreviewValueSource.WaitFor(Func`1 condition, Boolean disposing)
at Microsoft.Mashup.Evaluator.RemotePreviewValueSource.PreviewValueSource.get_SmallValue()
at Microsoft.Mashup.Evaluator.Interface.TracingPreviewValueSource.get_SmallValue()
at Microsoft.Mashup.Host.Document.Analysis.PackageDocumentAnalysisInfo.PackagePartitionAnalysisInfo.SetPreviewValue(EvaluationResult2`1 result, Func`1 getStaleSince, Func`1 getSampled)