This is a bug that AC seems to be aware of, and I think at one point they even reported that it has been fixed. I have a sense that it occurs less often than it used to, but is clearly still there.
I agree with Bert that you won't lose data by hitting "end task" in this setting.
Whenever this comes up, it leads to a discussion of when to turn off your computer, and when to turn off AC... issues which are otherwise pretty trivial (but which seem to evoke strong emotions from some). I see no reason to turn off AC daily. Sure, if your computer restarts for an update or whatever, you must restart AC. Otherwise, don't restart AC (just log out at the end of the day) and don't regularly shut down the computer, and you won't have to deal with this issue. Or at least, you will deal with it less often.
