rflickr/flickr GEM Conflict
It seems that there is a conflict between the rflickr and flickr GEMs. Basically this means that if you have both installed there is a good chance that it will use the wrong one. In my experience the flickr one tends to be used. The creator of rflickr is aware of this conflict (see https://rubyforge.org/forum/forum.php?forum_id=5509) but I don't know if ge has done anything to resolve this. Therefore you should make sure that you have run the following two commands if you want to use the rflickr GEM:
gem uninstall flickr gem install rflickr