ESB WCF Pipeline Error

I was receiving a very troubling error message when trying to submit a message to the ESB Bus through the ESB.ItineraryServices.WCF/ProcessItinerary.svc service.

ItinerarySelectReceiveXml – Verify the schema for this document specification is deployed and is in the Global Assembly Cache.

I thought I was going to have to reinstall the ESB Toolkit. It turns out all I needed to do was change the IIS Application Pool the WCF website was running on from .NET 2.0 to .NET 4.0. Apparently it was looking for the assembly in the 2.0 GAC rather than the 4.0 GAC.

Thanks to this forum thread for the solution!