`require': no such file to load -- activerecord

I'm trying to upgrade my Rails 2.3.5 app to Rails 3, and when I try
and start the rails server with 'rails s' I get this:

/Library/Ruby/Gems/1.8/gems/activesupport-3.0.3/lib/active_support/
dependencies.rb:239:in `require': no such file to load -- activerecord
(LoadError)

Using Mac OS X Snow Leopard, and it seems the error traces back to the
config.ru file in the first line:

require ::File.expand_path('../config/environment', __FILE__)

I copied this config.ru file from a fresh Rails 3 app.

Quoting Mike C <snibble@gmail.com>:

I'm trying to upgrade my Rails 2.3.5 app to Rails 3, and when I try
and start the rails server with 'rails s' I get this:

/Library/Ruby/Gems/1.8/gems/activesupport-3.0.3/lib/active_support/
dependencies.rb:239:in `require': no such file to load -- activerecord
(LoadError)

The file changed name to active_record, note the underscore. If you upgrade
from 2.3.5 to 2.3.x latest, it will let you know about such changes via
deprecation warnings.

HTH,
  Jeffrey

Thanks for the response! I don't manually include active record
anywhere, so how can I fix this?

Look at the stack dump. One of the Gems or plug-ins is requiring the file.

Jeffrey

Quoting Mike C <snibble@gmail.com>: