Just to make sure, for GWT compilation of a Vaadin widgetset, either by the separate compiler of the GWT development mode server, you need on the classpath:
the source code of the client side classes and
the compiled server-side classes (for scanning them for @ClientWidget annotations).
Not having the latter could be the issue here.
If not, the output of the GWT compilation (from the correct tab in the GWT development mode window) would be useful for troubleshooting this.
But I don’t understand from your post where I can specify how to find it.
I’ve already changed the class path of the GWT debugger as shown in my first post’s screenshot.