I had set my "time range to clear" on my clear history to everything. As soon as i pressed clear now, my computer had started lagging for some reason and two pop up had appeared on my screen that had three option, and was suggesting to stop script and stop plugin. I clicked on the suggested option's so it would stop the lag on my Mozilla, and i think i had accidentally checked off "form & search history" because it turned gray. Mozilla had began not responding after that and had no choice but to close Firefox. I got a new window and check if it worked, but i found out that my form & search history section, in my clear history details was gray and couldn't check the box. i tried clearing my cache and restarting Firefox to default if that would fix the problem, but it didn't. I checked privacy if it had a check mark on "remember form & search history," and it did, but the form & history section on clear history was still grey.