We updating to Autofac 2.4.4 after moving up to MVC3 and are receiving an exception when we include EnableInterfaceInterceptors on our registration. The exception does not appear until DependencyResolver.Current.GetService<ISite>() is called.
Exception:
Could not load type 'System.Func`2' from assembly 'App.AutofacContrib.DynamicProxy2, Version=2.4.4.705, Culture=neutral, PublicKeyToken=null'.
Registration:
builder.RegisterType<SendEmailTask>().As<ITask>().InstancePerDependency().EnableInterfaceInterceptors();
Note: In order to deal with conflicts in the different versions of Castle we performed an ILMerge on AutofacContrib.DynamicProxy2.dll and Castle.Core.dll.
Looks like a problem with the IL merge - rather than merging, have you tried assembly binding redirects?