Rails 3.0.0.beta Install problem: can't find executable rails

I'm trying to install the rails 3.0.0.beta and I'm running into this issue:

justins-mac-: justinz$ 开发者_StackOverflow社区ruby -v
ruby 1.8.7 (2008-08-11 patchlevel 72) [universal-darwin10.0]
justins-mac-justinz$ rails -help
/Library/Ruby/Site/1.8/rubygems.rb:384:in `bin_path': can't find executable rails for rails-3.0.0.beta (Gem::Exception)
 from /usr/bin/rails:19
justins-mac-justinz$ rails -v
/Library/Ruby/Site/1.8/rubygems.rb:384:in `bin_path': can't find executable rails for rails-3.0.0.beta (Gem::Exception)
 from /usr/bin/rails:19
justins-mac-justinz$ 

Any clues as to what is going on here?

sudo gem install railties --pre

After upgrading rubygems and cleaning up you need to:

gem install railties --pre

Try

sudo gem update --system

Since that does nothing, try

sudo gem cleanup

then reinstall.