Problem getting rails work :/

[hakermania]

By just giving rails in terminal (and every other thing rails command can do) the output is:

/usr/share/rails-ruby1.8/railties/bin/../lib/rails_generator.rb:30:in `require': no such file to load -- rubygems (LoadError)
from /usr/share/rails-ruby1.8/railties/bin/../lib/rails_generator.rb:30
from /usr/share/rails-ruby1.8/railties/bin/rails:14:in `require'
from /usr/share/rails-ruby1.8/railties/bin/rails:14

I have rubygems installed in the last version.
I followed this guide:
https://help.ubuntu.com/community/RubyOnRails
Thx in advance for any replies!