It is always hard to open the .rar file on MAC OS, most of the compression software on MAC have compatibility issue and u have to pay money for it.
The official Winrar for MAC don't have GUI (Command line only), hard to use for the MAC newbies, and Unrar X is a freeware with GUI but stop update since 2006. http://www.unrarx.com/
I have done some modify on the original Unrar X 2.2, upgraded the RAR core file to the latest version 3.93. Unrar has all the latest feature now, Enjoy it!
link:
http://www.megaupload.com/?d=6ZR7OR9B