An article I've been waiting for, on Developing Rails Applications on Mac OS X Leopard. Most important is that it has "official" update commands... myself being a total rails newbie I was glad to see this:
Out of the box, you get Ruby version 1.8.6 and Rails version 1.2.6, the latest stable releases at the time Leopard shipped. Ruby releases are few and far between (it's still at 1.8.6), but Rails has frequent new releases. In fact, the application we'll build requires Rails 2.0.2. The good news is it's easy to upgrade Rails and RubyGems. Make sure your system is up to date now by running these commands:
Instead of just hoping that running random commands would make it work. Coming from a Linux world of package managers where doing something "outside" the package world potentially pollutes the filesystem with outside code.