module in lib not included

On my production server, I get the error:

NoMethodError (undefined method `redirect_back_or_default' for
#<AccountController:0x2a96ffd698>):

This is from the login_generator gem. On my dev server (running
webbrick), this works fine. I've had my hosting company (A2) install
the gem and I've uploaded login_system.rb to my /lib directory.

I'm a newbie so forgive me if this question seems obvious.