Проблема с DelayActivity

Вот лог:
WinWF Internal Error, terminating workflow Id# 5eefb01d-6da3-47c2-9422-d59bd0529853 tem.Workflow.Runtime.Hosting.PersistenceException: Тип "Microsoft.SharePoint.SPGroup" в сборке "Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" не помечен как сериализуемый. ---> System.Runtime.Serialization.SerializationExceptio­n: Тип "Microsoft.SharePoint.SPGroup" в сборке "Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" не помечен как сериализуемый.
в System.Runtime.Serialization.FormatterServices.Int­ernalGetSerializableMembers(RuntimeType type) в System.Runtime.Serialization.FormatterServices.Get­SerializableMembers(Type type, StreamingContext context) в System.Runtime.Serialization.Formatters.Binary.Wri­teObjectInfo.InitMemberInfo()
в System.Runtime.Serialization.Formatters.Binary.Wri­t...
...eObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context,
SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter)
в System.Runtime.Serialization.Formatters.Binary.Wri­teObjectInfo.Serialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter)
в System.Runtime.Serialization.Formatters.Binary.Obj­ectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) в System.Runtime.Serialization.Formatters.Binary.Bin­aryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) в System.Runtime.Serialization.Formatters....
...Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph) в System.Workflow.ComponentModel.Activity.Save(Strea­m stream, IFormatter formatter) в System.Workflow.ComponentModel.Activity.Save(Strea­m stream) в System.Workflow.Runtime.Hosting.WorkflowPersistenc­eService.GetDefaultSerializedForm(Activity activity)
в Microsoft.SharePoint.Workflow.SPWinOePersistenceSe­rvice.SaveWorkflowInstanceState(Activity instanceState, Boolean unlock) в System.Workflow.Runtime.WorkflowExecutor.Persist(A­ctivity dynamicActivity, Boolean unlock, Boolean needsCompensation) --- Конец трассировки внутреннего стека исключений --- в System.Workflow.Runtime.WorkflowExecutor.Persist(A­ctivity dynamicActivity, Boolean unlock, Boolean needsCompensation) в System.Workflow.Runti...
...me.WorkflowExecutor.ProtectedPersist(Boolean unlock)