Ruby on Rails Gem error could not find gem

I got this gem error on Ubuntu 6.06 over and over then finally I followed these instructions to install Ruby on Rails, Install Ruby on Rails on Ubuntu 6.06 and I changed one line: sudo gem update –system IS WRONG!!!! run: sudo gem update and thing all the sudo gem installs work perfectly fine for me. Why I have no idea. I hate computers sometimes, but at least ruby and rails now work for Ubuntu 6.06 on my system.