Plugin breaking navigation jquery

We currently have this plugin installed on our site: http://www.sresusa.com/

The problem is that, when the plugin is installed, the dropdown menus in the navigation don’t work. Try clicking “About Us” or “Services” to see what I mean.

Is the plugin attempting to load its own version of jQuery? May this be conflicting with the standard navigation functionality?

Thanks.

http://ww.wp.xz.cn/plugins/optima-express/