I've noticed that even thought you close it sometimes the process keeps running in a hidden state. and if it keeps running it can start to consume MASSIVE amounts of CPU with out doing any thing.
I didn't notice that the process was still there one time and after three hours it was taking up 98% of my CPU (according to the process list) not only that but a normal end process command won't get rid of it you have to kill it.
I just thought I would point it out and say that perhaps we need find a way to be sure the process gets killed.
NOTE that this has happened in both Windows and Ubuntu