Events + plugin - breaking page navigation

Top nav tabs which are linked to normal pages return "Page not found" when Events is activated...the page loads on 2nd click.

This happens when you go from "Groups" - which is a core Buddpress page - to pages we have created in Admin

Deactivate the plugin - the pages load fine.

Tried everything we can think of...any ideas?

Done permalinks, checked htaccess file etc etc