Render system config window crash on linux.

Original reporter: Diamond145

Using revision 1618da2b6b00.
Built with g++ version 4.6.3 on Ubuntu 12.04 x86_64.
Using background threading with the boost (1.46.1) provider.

Steps to reproduce:
1. Start ./SampleBrowser
2. When the render system config window opens, click on "Select One".

Original Mantis Ticket: http://www.ogre3d.org/mantis/view.php?id=544