Trouble loading rails generated javascript to view

I've been following Ryan's recent railscast on creating dynamic select
menus using javascript:

He suggests the following method to create and load rails generated

1. create a 'javascripts' controller
2. create a method within that controller
3. create a file called method_name.js.erb in app/views/javascripts
4. use an application helper method in the view to load the javascript
in the head.

I've gotten javascripts/method_name.js to render properly in my browser.
It appears to load into my view with this helper method:

<script src="/javascripts/method_name.js"

The script doesn't seem to load however. The html source doesn't confirm
much since I can get it to reference non-existent javascripts without
error. Any idea what might be preventing the load or what I could check
to get a better idea of what's going on?