Microsoft recently released the Service Pack 2 and August 2013 cumulative updates. There are some installation issues if you try to install August 2013 CU after installing Service Pack 2. Microsoft is working currently on it and will have fix available shortly. You can find the additional information at Brian Smith’s blog

http://blogs.technet.com/b/projectsupport/archive/2013/09/12/project-server-2010-service-pack2-and-august-2013-cumulative-update-installation-issues.aspx