Web Player Serialization Broken

I have a very simple class I wish to deserialize:

 [DataContract]
 public class SerializationTest1
 {
     public SerializationTest1()
     {
     }
 }

But when I do it produces this error:

 MethodAccessException: Attempt to access a private/protected method failed.
   at System.Security.SecurityManager.ThrowException (System.Exception ex) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.SerializationMap.DeserializeContent (System.Xml.XmlReader reader, System.Runtime.Serialization.XmlFormatterDeserializer deserializer, Boolean empty) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.SerializationMap.DeserializeEmptyContent (System.Xml.XmlReader reader, System.Runtime.Serialization.XmlFormatterDeserializer deserializer) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.SerializationMap.DeserializeObject (System.Xml.XmlReader reader, System.Runtime.Serialization.XmlFormatterDeserializer deserializer) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.XmlFormatterDeserializer.DeserializeByMap (System.Xml.XmlQualifiedName name, System.Type type, System.Xml.XmlReader reader) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.XmlFormatterDeserializer.DeserializeCore (System.Type type, System.Xml.XmlReader reader) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.XmlFormatterDeserializer.Deserialize (System.Type type, System.Xml.XmlReader reader) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.XmlFormatterDeserializer.Deserialize (System.Xml.XmlReader reader, System.Type type, System.Runtime.Serialization.KnownTypeCollection knownTypes, IDataContractSurrogate surrogate, System.String name, System.String ns, Boolean verifyObjectName) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.DataContractSerializer.ReadObject (System.Xml.XmlDictionaryReader reader, Boolean verifyObjectName) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.XmlObjectSerializer.ReadObject (System.Xml.XmlDictionaryReader reader) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.DataContractSerializer.ReadObject (System.Xml.XmlReader reader) [0x00000] in <filename unknown>:0 
   at System.Runtime.Serialization.XmlObjectSerializer.ReadObject (System.IO.Stream stream) [0x00000] in <filename unknown>:0 
   at Deserialize[SerializationTest1] (System.String data, Boolean compressed) [0x00000] in <filename unknown>:0 
   at Deserialize[SerializationTest1] (System.String data) [0x00000] in <filename unknown>:0 
   at RunTests () [0x00000] in <filename unknown>:0 

Is Web Player deserialization just totally and completely broken? It certainly seems that way to me.