That's DEFINITELY a dump cache, history and all online temp files issue.
My computers are scheduled to automatically do that every 24 hours minimum. But I do it also about every 8 hours or so just so I don't have clogging up problems when viewing images, entering sites and such.
I use this software...it's good with Firefox, IE, Opera and handles cleaning up EVERYTHING.
Don't forget to reboot.
Hope this works for you.
Take care, Donna