Re: "You can't open the application The Sims™ 3 Installer because PowerPC applications are no longer supported."

Just purchased newest expansion and it won't install on my OSX 10.8.2.  I get this message, "You can't open the app because PowerPC applications are no longer supported".  I have other expansions, all up to date, and have never had a problem.  It says that it should run on an up to date Mac system, which mine is, so what gives?  Can I get this to work or not?