This issue has been discussed before (http://www.ruby-forum.com/topic/ 125392) and after spending a while debugging through this, I still don't have a solution. Lets try again?
I have two controllers, SomeController and Admin::SomeController. When SomeController is loaded first (which happens under spork, found out by editing ActiveSupport::AbstractController) I get warning: toplevel constant SomeController referenced by Admin::SomeController and the second controller is not loaded. The first controller is polluting something for the namespaced controller.
I have a rather large project where this happens, so I can't post it. But I have a 100% repro, so I'd be happy to do some debugging.