Glav posts about a problem I've also had recently - that Matt helped me figure out how to solve. The exception is (repeated here for seach purposes): This collection already contains an address with scheme http. There can be at most one address per scheme in this collection. Parameter name: item Description : An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.ArgumentException: This collection already contains an address with scheme http. There can be at most one address per scheme in this collection. Parameter name : item The way to solve this problem is to setup multiple web sites in IIS (rather than having one site that has multiple Host entries) - and point all the websites to the same directory. Hope this helps someone. Check out my BizTalk R2 Training . Read More...