if you install the RubyInline gem and image_science and are having problems...
remove your .ruby_inline directory and run this sed one-liner.
sudo sed -i -e "387,1s/flags\ =\ @flags.join(\'\ \')/&\ \+\ \'\ -lruby\'/" /usr/lib/ruby/user-gems/1.8/gems/RubyInline-3.6.4/lib/inline.rb
for more info on this issue see:
http://trac.macosforge.org/projects/ruby/wiki/Troubleshooting
