Can't install rake on Mac OS X: undefined method `map' for nil:NilClass

I'm having the worst time trying to install rake. Every time I start rake I get "undefined method `map' for nil:NilClass". I hear solutions exist, such as installing older versions of rubygems, but to do so I can't use macports and life starts sucking again.

ruby 1.8.7 (2010-08-16 patchlevel 302) [i686-darwin9]
gem 1.3.7
rake, version 0.8.7

All installed with macports.

Any suggestions? I've been putting apt-get and macports up against each other in different fights, but that didn't work out, so now I'm putting all my money on macports.

Oh, I am on Mac OS X Leopard (10.5).

And the trace starts with:

/opt/local/lib/ruby/site_ruby/1.8/rubygems.rb:223:in `activate'
/opt/local/lib/ruby/site_ruby/1.8/rubygems.rb:249:in `activate'
/opt/local/lib/ruby/site_ruby/1.8/rubygems.rb:248:in `each'
/opt/local/lib/ruby/site_ruby/1.8/rubygems.rb:248:in `activate'
/opt/local/lib/ruby/site_ruby/1.8/rubygems.rb:1082:in `gem'
...

Solution

Have you tried homebrew instead of macports? It's a package manager that works with OS X 10.5 or later. I've been using it in conjunction with RVM to handle various Rubies and gemsets and it's worked out great.