It's likely you're missing some of the changes to the config files that you need in Rails 3 and your intitializer isn't being included. I made the same upgrade recently, you can check my changes. There's a lot of changes there that won't be useful to you, but pay attention to any changes to files at the root of the application and under config
.
Also, make sure you have your app name (matching the initialize!
line in config/environment.rb) and not "MyApp".