[Exchange-Online][EWSMA][C#][Windows]: Assistance with AutodiscoverLocalException Error

To start off I have spent the last two hours looking through the older posts to find the answer to this one, so I apologize if I've overlooked it.

I developed a Middleware Web Service that our ticketing system can call to put appointments on our Live@EDU (Exchange Online) calendars.  I developed this in Visual Studio 2010 on Windows 7 behind a proxy service.  It worked great on that platform when I deployed it to the localhost.

I've now since deployed it on our development application server (Windows 2008 R2, IIS 7) which is also running through the same proxy service, and I'm getting this error when running my web service method:

Microsoft.Exchange.WebServices.Data.AutodiscoverLocalException: The Autodiscover service couldn't be located.
   at Microsoft.Exchange.WebServices.Autodiscover.AutodiscoverService.InternalGetLegacyUserSettings[TSettings](String emailAddress, List`1 redirectionEmailAddresses, Int32& currentHop)
   at Microsoft.Exchange.WebServices.Autodiscover.AutodiscoverService.GetLegacyUserSettings[TSettings](String emailAddress)
   at Microsoft.Exchange.WebServices.Autodiscover.AutodiscoverService.InternalGetLegacyUserSettings(String emailAddress, List`1 requestedSettings)
   at Microsoft.Exchange.WebServices.Autodiscover.AutodiscoverService.GetUserSettings(String userSmtpAddress, UserSettingName[] userSettingNames)
   at Microsoft.Exchange.WebServices.Data.ExchangeService.GetAutodiscoverUrl(String emailAddress, ExchangeVersion requestedServerVersion, AutodiscoverRedirectionUrlValidationCallback validateRedirectionUrlCallback)
   at Microsoft.Exchange.WebServices.Data.ExchangeService.AutodiscoverUrl(String emailAddress, AutodiscoverRedirectionUrlValidationCallback validateRedirectionUrlCallback)

I can run the test for Web Services on 'http://testexchangeconnectivity.com' without a problem.  Any idea what might be occurring?  This server is a lot more locked down than my desktop where I developed it initially, and I have a feeling it's firewall (local or edge) related, but I'm not sure.

My next step is to run a WireShark trace and see what is happening, but I was hoping someone else might have run into this situation before as well.