Cannot upgrade RubyGems

Question

Why is the following happening, and how can I sort it?

On OS X Leopard (v10.5.6):

$ ./script/server 
Rails requires RubyGems >= 1.3.1 (you have 1.2.0). Please `gem update --system` and try again.
$ sudo gem update --system
Updating RubyGems
Nothing to update

Answer 1

I haven't hit this issue myself but I've seen this as a possible solution:

$ sudo gem install rubygems-update
Successfully installed rubygems-update-1.3.0
1 gem installed
$ sudo update_rubygems

This should let you install the updating via the specific updater gem.

Referenced here: updating rubygems