WPMU Dashboard install shutting down my back-end

I downloaded the latest version of the plugin. Installed it through the plugin installer upload and install, and when wordpress installs the dashboard, I cant access the back-end anymore. I get a 500 error and It says "page isn’t working"

This is a new site I'm building, so it doesn't have many plugins a I never had any problems before with any other of my sites. Not sure what is going on.

I've renamed the plugin in the plugin directory so that I can continue accessing the back-end. Any feedback would be greatly appreciated.

Website: bullseyeinternet.com