Have you ever seen this error? System.IO.FileLoadException: Could not load file or assembly ‘nameOfAssembly’, Version=specificVersion, Culture=neutral, PublicKeyToken=publicKey’ or one of it's dependencies. The located assembly’s manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) This means you’ve replaced the specific version of the third party assembly with either an earlier or an updated version. The assembly that uses it is compiled to point to a specific version of the assembly and now will not load. I’ve seen this the most with applications that use log4net and/or NHibernate and third party assemblies that also use log4net and/or NHibernate.