Permalinks working infrequently

In our Events Widget and on the Events page, the links to each event’s page are working sporadically: I can click the link and get “Page Not Found,” then return and the page will show up.

When I go into the admin area and click “View” on an individual event, the page loads fine.

Any ideas?

Website: http://www.gaytonchurch.org

http://ww.wp.xz.cn/plugins/events-manager/