A few days ago we noticed some strange errors popping up on one of our applications, it turned out to be a rather nasty naming clash between a controller and an actionmailer. http://dev.rubyonrails.org/ticket/3681 I don''t really have time to dig into all the rails internals to see where this is going wrong, perhaps somebody with a little bit more knowledge about the lazy class loading can pick this up? Manfred