A few days ago I noticed that a site (which I built but whose content is maintained by someone else) needed a whole bunch of updates, so I did them (I don't think there was a core update - auto update is on, so it should have already been at 4.4.2). A quick glance at the site looked okay. But the content person informed me of problems trying to do maintenance, and I discovered that any "Add New" (Posts, Pages, and a couple of custom post types that I have) results in "Error 500 Internal Server Error". I do have a number of complex plugins, but I still get the error with all of them disabled.
My hoster is unfortunately still running PHP version 5.2.9. Wordpress claims to still be compatible with it, but could that be an issue anyway? Or what else should I check? I really expected a plugin to be at fault, but apparently not.