Plugin crashes homepage and website

Hi, We're using Supermassive from themeforest.net. When we install the Wordpress Membership plugin, it crashes the site. The admin section stays in tact, but the front end goes down. It's only showing background, logo and nave bar - no navigation and content. Could this be a stylesheer error? We noticed it works in Chrome, but dumps in FF, IE and Safari. Can you help me out? Thanks! - Bill