Error when updating pages - Only when WP Meta SEO Plugin active

We have this installed and I have a question.

When I try to update text on a page and click Update - I get the following error.

This page isn’t working momsorganicmarket.com is currently unable to handle this request.
HTTP ERROR 500

It looks like the change actually gets made, but the error makes it seem like it hasn't changed.

This only happens when I have the WP Meta SEO plugin active