Blogs Directory Error: Invalid Page

I just noticed that our Blogs Directory page displays nothing but an "Invalid Page" error.

With the plugin deactivated, page loads fine with all content. Once activated, the page is blank.

I deactivated the plugin, and added a notice to the page, but the link is

I have reactivated, and even replaced the plugin files, v. Error was first noticed after recent upgrade to WP 4.0. Theme is WPMU Nelo.

Any suggestions are greatly appreciated. Thank you!