Firefox Internet Cache Skipped

For the past two days, when I "Run Cleaner" it comes back with "Firefox Internet Cache Skipped." Why is it doing this?

do you still have Firefox, or some Firefox process (check Task Manager) running ?

Firefox.exe and plugincontainer.exe both need to be stopped for CCleaner to run. CCleaner should prompt you to close them if they're running so long as you didn't check the box that says 'never ask again'

Thank you winapp... only problem is I don't think CCleaner has ever prompted me to close them and I don't know how to "stop" them. One interesting point is that after I posted this yesterday... I ran CCleaner and it DID clean Firefox. But then when I ran it again this morning, it skipped it again. Seems to be sporadic. What can I do before I run it (stop) so that it won't skip Firefox... because Firefox seems to be my biggest problem. I love Firefox but I always seem to have issues with it. :(

end firefox.exe from the task manager or by running

taskkill /f /im firefox.exe

Thank you!