NServiceBus "CreateBus()" returning null - msmq

Question

I am using NServiceBus 2.6.0.1504 on windows server 2003 32 bit.
The log file generated indicates that everything is getting wired up, but for some reason, "CreateBus()" returns null. Ignore my debugging code :)
SetLoggingLibrary.Log4Net(log4net.Config.XmlConfigurator.Configure);
var one = Configure.With(typeFinder.GetAssemblies());
var two = one.DefaultBuilder();
var three = two.MsmqSubscriptionStorage();
var four = three.XmlSerializer();
var five = four.MsmqTransport();
var six = five.IsTransactional(false);
var seven = six.PurgeOnStartup(true);
var eight = seven.UnicastBus();
var nine = eight.LoadMessageHandlers();
var ten = nine.ImpersonateSender(false);
var eleven = ten.CreateBus();
if (eleven == null)
throw new Exception("createbus");
var twelve = eleven.Start();
The exception with the message "createbus" always gets thrown.
This works on my dev box with is Windows Server 2008 R2 64 bit.
Here is my config for the web app.
<MsmqSubscriptionStorageConfig Queue="MedXChangeSubcriptions" />
<MsmqTransportConfig InputQueue="MedXChangeForms" ErrorQueue="error" NumberOfWorkerThreads="1" MaxRetries="5" />
<UnicastBusConfig>
<MessageEndpointMappings>
<add Messages="MethodFactory.MedXChange.Library" Endpoint="MedXChangeWeb" />
</MessageEndpointMappings>
</UnicastBusConfig>
Any ideas? Any help would be greatly appreciated.

Answer 1

NServiceBus will return null if a bus has already been created. So determine if someone is already instantiating a bus for you.
In my scenario, we were inconsistently defining endpoint configurations. In one process, we would implement IConfigureThisEndpoint and then explicitly configure and instantiate a bus. In another process we would inherit from AsA_Publisher which implicitly creates a bus for you; and when it came time to explicitly define our bus' configuration for this other process we would throw NullReferenceException on the fluent CreateBus method. Removing the AsA_Publisher inheritance resolved the issue.
Hope this helps!