MessagingException was unhandled

I was trying the service bus 1.0 for windows on a development machine. I set up a virtual environment based on windows server 2008 R2 SP1 with SQL Server 2008 R2 SP1 and Visual Studio 2012. I configured the service bus following the steps described at the following link (Getting started with the Service Bus for Windows Server):  

http://msdn.microsoft.com/en-us/library/windowsazure/jj193021(v=azure.10).aspx

I wrote the console application copying the code from the tutorial at this link (Step2: Write Your First Program):

http://msdn.microsoft.com/en-us/library/windowsazure/jj542433(v=azure.10).aspx

When I arrive to the line of code highlighted in bold: 

string QueueName = "ServiceBusQueueSample";
if (namespaceManager.QueueExists(QueueName)) <--MessagingException{
    .......
}

I have a MessagingException with the following message:

"The token provider service was not avaliable when obtaining a token for 'https://MyServerName:9355/ServiceBusDefaultNamespace/$STS/Windows/'"

and an InnerException with the following message:

"The remote server returned an error: (503) Server Unavailable"

Everything is running on the same machine (the service bus and the console application). Could someone shed some light on the nature of the problem?

Thanks for any suggestion.