I was using WP Super Cache until my site began displaying blank pages. After uninstalling the plugin, site content returned, but Ajax was botched. Anytime Ajax had to update content, I would see spinning arrows until manually refreshing the page displayed the proper content.
After removing all WP Super Cache entries from .htaccess and removing files left behind after deleting the plugin, my site works again.
Just posting in the hopes that this might alleviate the headaches of others. A great many Contact Form 7 and All in One Event Calendar users are experiencing much grief right now.