After running WCF on my Vista laptop (IIS7) I needed to deploy the application on some Windows XP computers. Again some strange errors occurred:
Error Description: "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 problem is that WCF cannot handle more than one identity (host headers) per website. At first I configured IIS to have one HostHeader. That solution was just to dirty. So I kept on searching the internet.
You can fix this problem by adding prefix-key(s) in the baseAddressPrefixFilters section of the Web.Config:
Hope this helps.