Amongst all the fun I had with moving this site to a new server, I attempted to install updates to my Macbook Air, and in the process managed to hose it up pretty good. Fortunately, I didn't have any real data on it, so after trying a few troubleshooting steps, I just erased the drive and re-installed Yosemite, then I upgraded to El Capitan. For all practical purposes I have a fresh new OS on the Air, so it's not all bad.