Incompatibility with other important plugins

When you say content ceases to display, do you mean that the page is completely blank? That usually means there’s a PHP error of some kind. Please check your PHP error log for recent messages related to any of the involved plugins.

(If you don’t know where to find the error log, ask your hosting provider.)

Many thanks for pointing me in that direction! That is exactly what it was — an invalid argument on a foreach() function in plugin.php. Not your issue, obviously, but thank you for helping me find it.