This means that the process never did finish. For some reason the task is still running. Check your logs to see if you see something amiss. Killing the request does in my opinion not help (I have almost never seen this working, refreshing would always give the process again). The only way to solve this is to reset the server.
Check the microflow which it is running, is that microflow running a process that is using $currentUser ? the 6.8 and 6.9 versions had some trouble with the $currentUser variable that resulted in microflows never finishing.
Edit:Looking more carefully at your screenshot it looks like the action itself has already been killed but the session was not killed. This situation can occur when you have a memory overload i.e. when your os decides to kill a random process, perhaps it killed your action but not the complete session?