I noticed this the first time on my first sylvan character. I received a notice that the game would be updating in 50 minutes when I started, and once I got my character (a sylvan) to the boss in the intro (only a few minutes later), the moment the boss was killed, it ejected me. I came back in and had to kill the boss a second time. While waiting for it to load, it appears the update to my client side happened.
The next day, I was in a Personal Story quest, saw a similar update message, and when I accomplished the goal of my quest, it ejected me once again. Fortunately this time I did not have to repeat it.
