I just got the weirdest glitch! I am dead, but I can still run around, and nothing can see me - and I can't hurt anything.
I'm afraid the screen recording program I have does not work with the Unity player so I can't make a video, but
here is a screenshot. You can see I have zero life force. The advantage of it is I can now run and explore anywhere I want without being attacked, but I probably can't actually interact with anything. I'm guessing I will have to exit and restart the game to fix it. Of course I have no idea what caused it, I'm sure it was random.
edit: I think this was just a variation of the "Network Close" error where I lost connection with the server; however when it first happened there WERE still monsters and NPCs present, and I could bash at the monsters all I wanted without them noticing me. I finally did get the Network Close popup.