I've just updated to OS X Mountain Lion and I'm getting the following when working with rails and terminal.
WARNING: Nokogiri was built against LibXML version 2.8.0, but has dynamically loaded 2.7.8
I've had a look at other answers to a similar question, but they doesn't seem to stop the warning message from appearing.
I was having similar issues installing nokogiri gem on ruby 1.9.2 Apparently Apple upgraded gcc... I fixed this with a symlink and then the gem installed just fine:
sudo ln -s /usr/bin/gcc /usr/bin/gcc-4.2