I installed Pro Sites and now I can't access my site!?!

Hi! I just installed Pro Sites on my site, and now I'm not able to see my site. Here is the error that comes up when I go to my front page:

Warning: require_once(/home/dspinner/public_html): failed to open stream: No such file or directory in /home/dspinner/public_html/wp-content/plugins/marketpress/includes/addons/class-mp-addons.php on line 81

Fatal error: require_once(): Failed opening required '' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/dspinner/public_html/wp-content/plugins/marketpress/includes/addons/class-mp-addons.php on line 81

Here is the error that came up originally when I was on the plugins page:

Warning: require_once(/home/dspinner/public_html/wp-admin/network): failed to open stream: Success in /home/dspinner/public_html/wp-content/plugins/marketpress/includes/addons/class-mp-addons.php on line 81

Fatal error: require_once(): Failed opening required '' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/dspinner/public_html/wp-content/plugins/marketpress/includes/addons/class-mp-addons.php on line 81