The following pops up too often when using firefox (50.1.0): "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." A superficial search shows this has been a common problem, but no definite solution offered. Appreciate any suggestions.
Looks like the Firefox doesn't close its window properly.
killall -9 firefox
The problem isn't with closing Firefox. It is the opposite. I want to keep a firefox window open and then at the same time open other firefox windows. It won't let me do that. Oh, well, have installed SRWare Iron and am using it at the moment. May get back to Firefox in the future, or may not. Iron works nice and is very fast.
Firefox have been a bit ??? lately. But it does not irritate me enough to do something about it, else than wait for it to get better. :)