I have been receiving this error recently with a web site I was developing. Its rather weird because I am not using it nor had I any reference to System.EnterpriseServices or anything else that might have. In fact the web site was new so didn’t have much of a reference to anything except the default assemblies. Well a little searching turned up that the there was a reference to the System.EnterpriseServices assembly in the web.config located in the “C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\CONFIG” folder.
How it got there? I can only assume it’s the result of recently installing the Microsoft Enterprise Library. Now that was about a weeks ago but its quite possible that I didn’t do any other ASP.NET development since. Whatever the cause was, if you receive the same error that is one thing you might want to check.
Maurice de Beijer