I downloaded the nServicebus binaries as of May 17th and have two different vb.net projects (one in .net 3.5, the other in .net 4.0) that both have the error "Reference to Assembly nServicebus, Version 2.0.0.1145, culture=neutral, PublicKeyToken=9fc386479f8a226c containing the type NServicebus.IStartable. Add one to your project. I have in the references already nServicebus.dll, nservicebus.Core.dll, and log4net.dll