After upgrading to the newest version of rails (2.2.2) I was getting this error:

administrator@shuttle:~/$ gem -v /usr/bin/gem:10:Warning: Gem::manage_gems is deprecated and will be removed on or after March 2009. /usr/bin/gem:23: uninitialized constant Gem::GemRunner (NameError)

Anytime I called "gem" I would get this error and could not get past.

Here is the fix

administrator@shuttle:~/$ sudo vim /usr/bin/gem

Change the top of the file to look like this:

require 'rubygems' require 'rubygems/gem_runner' #Gem.manage_gems

Save and when you run this you should see this:

administrator@shuttle:~/$ gem -v 1.3.1

You should no longer get the error with running "gem"