Rails question; 0.13 upgrade woes

OK, Rails folk, I need some help. We upgraded to Rails 0.13 yesterday and have run into some problems.

Prior to the uprade, we had URLs that looked like this: http://localhost.example.com:3000/MyAccount/login and they worked correctly. After the upgrade, these URLs return an error ("Routing Error. Recognition failed for ./MyAccount/login'"). However, the URL http://localhost.example.com:3000/my_account/login now works.

Anyone have an idea what happened? My best guess is that has something to do with the new routing features, but I don't understand enough to go dig into it. Any help would be most appreciated.