Not sure why I\'m getting this, but I just installed RVM, the new Ruby 1.9, and reinstalled a bunch of gems, and I get this
/Users/johnsmith/.rvm/rubies/ruby-1.9.1-
Just chmod go-w /opt/local/bin at a shell prompt (depending on permissions you may need to sudo to do that).
chmod go-w /opt/local/bin
sudo