I recently upgraded Muziboo to Rails 2.3 and found out that some of my routes were broken. On digging deeper I found out that I had some routes with two version, one without :format and one with :format going to different controllers/actions. I had the route with :format before the route without :format in the routes.rb file and changing the order fixed the problem. I am not sure why this happened but its been working fine since the change. If you run into routing issues, do try this and let me know if it worked for you.