Yes, if the timer is 5 hours then you'll have to wait until 5 hours after that active one expired. It is quite annoying getting screened out of a google survey since you are forced to return it and get locked out of any other google stuff through no fault of your own. I haven't seen this recently but it is possible to do everything right and end up "locked out". I.e. just working from your queue and you get the error message. Try reloading the HIT, might fix it. (There is even a script for it somewhere.) I think this happens if the new hit tries to load before their system registers the old one has been completed -- a second or two later it loads fine. This is rare and I haven't had it happen recently so maybe they fixed it.