this now happend to me twice. My phone just shut off and started on its own again but the message poped up that apps are being updated. What happend was, that for some reason the phone went back to dalvik. I have set it to ART and was running it for a long time now. This happended today. Many apps broke and were uninstalled and when I tryed to install them again a error messaged popped up (error code -110 or something).
So I wiped the whole phone via recovery and began to install everything fresh. I also changed to ART before installing anything. While I was doing that, about 30 minutes later, the same thing happend again. And again it went back to dalvik. I don't know what is going on here or what is causing this. I was running android with ART for some months now and I never had any problems.
I'm running the stock rom (4.4.4) but rooted with towelroot. bootloader/recovery is the one the phone came with and it's locked.