MSMQ Serializable Hashtable subclass causes a hang when extracting Message.Body

To start:  I get no error message; just a hang condition.  If I could get an Exception, I could probably figure this out for myself.  Instead, .NET just hangs, cold and unresponsive.< xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Here's the short concept of what I'm doing (no code examples here as the concept should be simple enough to implement by any interested troubleshooters):

1. Make a struct called KeyValuePair with two fields:  a Key and a Value, both String types.  Mark the KeyValuePair struct as [Serializable].
2. Make a subclass of Hashtable called HashSet and override the Add method to guarantee that all Keys are unique at all times when Add(key, value) is used.  Mark the HashSet subclass as [Serializable].
3. Make a subclass of HashSet called SpecializedHashSet.  Overload the Add method to receive a KeyValuePair struct and forward the field data to the other Add method (of HashSet).  Mark SpecializedHashSet as [Serializable].
4. Make a subclass of ArrayList called ArraySet and override most of its methods to also guarantee that its values will always be unique within the array.  Mark the ArraySet subclass as [Serializable].
5. Create a new class that will be part of a bigger package that will be created in the next step.  Call it PackageWrapperComponent and add a few simple properties (Int32, Boolean, and String).  Add also a SpecializedHashSet property.
6. Create a new class that will be the package wrapper you intend to send via MSMQ from client to server.  Call it PackageWrapper and give it a few simple properties and one ArraySet property.  Also add a PackageWrapperComponent property to hold a reference an object of the class written in step 5.
7. Create two simple console application projects, both with references to the project containing the code written for steps 1-6:  one to send the MSMQ message and one to receive the MSMQ message.  The two applications will run on two physically separate machines.
8. The Client will create a PackageWrapper, set all property values (including a fully populated PackageWrapperComponent), and send the PackageWrapper via MSMQ to the server in a BinaryMessageFormatter message.
9. The Server will receive the message and attempt to extract the PackageWrapper from the MSMQ message body.

At this point, .NET hangs on the server when all properties are initialized.

I can avoid the hang by NOT initializing the SpecializedHashSet property of the PackageWrapperComponent of the PackageWrapper object.  In other words, when the SpecializedHashSet instance is left null on the PackageWrapperComponent, everything works.  But once I initialized SpecializedHashSet, even to an empty SpecializedHashSet, the server hangs when it attempts to extract the message body.  Additionally, if I demote the SpecializedHashSet to a Hashtable, everything works, even when initialized.  Naturally, I need to use SpecializedHashSet and not Hashtable in my production code.  Is there some serialization/deserialization condition which prevents developers from working with subclasses of Hashtable   Or am I (hopefully) just missing some mundane detail

I have wrapped the particular server code in a try/catch block, but no Exception is ever thrown.  .NET just hangs cold.  I have placed extensive debugging WriteLine() lines around the code and have isolated the line that hangs:

public void AcceptAsyncMessage(Object source, ReceiveCompletedEventArgs asyncResult) {

      MessageQueue msmqEventQueue;

      Message msmqMessage;

      Object messageBody;

      Console.WriteLine("Woken up by MSMQ.  Attaching to the local Microsoft Message Queue to receive the message...");

      // Connect to the queue.

      msmqEventQueue = (MessageQueue)source;

      Console.WriteLine("Connected to the local receiving Microsoft Message Queue.");

      // Momentarilly end the asynchronous Receive operation to extract the message body.

      try {

            Console.WriteLine("Extracting the message entity...");

            msmqMessage = (Message)msmqEventQueue.EndReceive(asyncResult.AsyncResult);

            Console.WriteLine("Extracting the message body...");

            // .NET hangs right here:

            messageBody = msmqMessage.Body;

            Console.WriteLine("The message body has been retrieved.");

      }

      catch (Exception e) {

            Console.WriteLine("Exception encountered:  {0}", e.Message);

      }

      // Further code which analyses and processes the messageBody has been omitted as it is never reached.

}

I see all Console messages up to "Extracting the message body…", but I see neither "The message body has been retrieved." nor "Exception encountered:".  .NET freezes when attempting to assign the Message.Body value to an Object variable.  What's up   It may be only my opinion, by I feel that .NET should -- at least -- throw an Exception rather than hang like this.  How do I make this work

My environment:

Microsoft Visual Studio 2005 (C#.NET)

Microsoft .NET 2.0

Microsoft Windows XP Professional on both Client and Server (for now, will be on Windows 2003 Server when this project moves to production).

While I'd love to provide all my actual code, I cannot for proprietary reasons and because, frankly, there are many hundreds of lines of code implementing this simple concept in my real application.