CGI::Session::ActiveRecordStore

if you upgrade to Rails 2.3, the session management has
changed significantly, per the release notes:

CGI::Session::CookieStore has been replaced by ActionController::Session::CookieStore.
CGI::Session::MemCacheStore has been replaced by ActionController::Session::MemCacheStore.
CGI::Session::ActiveRecordStore has been replaced by ActiveRecord::SessionStore.