Using Gems with Ruby On Rails: Undefined method?

There's this snazzy captcha that asks questions rather than displaying pictures. You can read about it at textcaptcha.com. Anyway. I want to use that with Ruby on Rails. A developer by the name of Matt Hutchinson wrote a Gem for easily connecting to the API. He has a set of instructions next to his source files on github. Anyway, It looks pretty simple but in trying to implement it I get this error every time:

undefined method `acts_as_textcaptcha' for #<Class:0x104098508>
Rails.root: /Users/cory/Documents/Learning/RoR/dpt

Application Trace | Framework Trace | Full Trace
app/models/citation.rb:20
app/controllers/citations_controller.rb:29:in `new'

The root of my question has a bit less to do with this specific gem, and a little more with how gems work. I've installed the gem, and then bundled it inside of my rails app, it should be accessible (as I understand it). I see references to the gem in the gemfile.rb and the gemfile.lock, but again and again it tells me I'm using and undefined method.

The gem should be defining the method for me, should it not? Or is there something that I manually have to do?

Just let me know if there is any other info that would be helpful, thanks!

Well, jeez. It's working now. It could be that I restarted the server, but I'm not positive. What I did was installed RubyMine to see if I could use it's debugger, in doing so it required that I run the bundle install (it chose some different versions of some dependancies) through there, and also stop my other webrick server, to run the one through the RubyMine console. I did so, it gave me errors, when when I went back to my other installer it worked!? Anyway, I've got my question resolved, but in the event that anyone looks this up, these are my current gems:

$ bundle install
Using rake (0.8.7) 
Using abstract (1.0.0) 
Using activesupport (3.0.0) 
Using builder (2.1.2) 
Using i18n (0.4.2) 
Using activemodel (3.0.0) 
Using erubis (2.6.6) 
Using rack (1.2.1) 
Using rack-mount (0.6.13) 
Using rack-test (0.5.7) 
Using tzinfo (0.3.24) 
Using actionpack (3.0.0) 
Using mime-types (1.16) 
Using polyglot (0.3.1) 
Using treetop (1.4.9) 
Using mail (2.2.15) 
Using actionmailer (3.0.0) 
Using arel (1.0.1) 
Using activerecord (3.0.0) 
Using activeresource (3.0.0) 
Using bcrypt-ruby (2.1.4) 
Using acts_as_textcaptcha (2.2.0) 
Using bundler (1.0.10) 
Using thor (0.14.6) 
Using railties (3.0.0) 
Using rails (3.0.0) 
Using sqlite3-ruby (1.2.5) 
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.

Thanks all! But if you are trying this, do try restarting the server first as suggested, I wish I knew if that would have worked :D