Apparently this blog was down for two days, and I didn’t notice. 
The problem came courtesy of a tracking a trunk checkout of a plugin. A change got checked in which broke some functionality I was using, and when I updated I picked up the change and didn’t check my site.
I really should know better. My only excuse: I have been out of the office for a couple of days and busy working for clients.
Yes, of all people you should have known better.The plugin “Plugin Test Drive” has saved many a site since it became available. Even if only testing a plugin upgrade for a few minutes after an update saves misery. The newestsWord Press version does have better tolerance for nasty surprises and will deactivate a troublesome plugin and when repaired [if possible] allows easy reactivation. So thank you for that improvement.