Intellij Ruby Plugin Setup

I tried to install Intellij Ruby Plugin on Mac OS X Leopard. Following the instruction, the installation was fairly straight forward. Then I tried to add Ruby SDK into the plugin. I started with /usr/lib/ruby, /usr/bin/ruby, /usr/bin as home directory, and got "The directory selected is not a valid home for Ruby SDK". What?...My ruby installation does exist in this directory. Actually, Ruby SDK home path has to be /usr

Hope this will save you some time...

BTW: Intellij collapsed twice after I set up the ruby plugin. Not sure what's going on there.