Making sure you're closed out of every browser, uninstall Flash. Restart. Once again making sure you're closed out of every browser, reinstall Flash and restart again. Then check how Flash is doing in Firefox. Oh, and make sure the version of Flash you're installing is the standalone plugin for Firefox/Netscape browsers. I went through this same thing about a month ago, lol.
I INSTALLED the new quicktime the other day and now everytime i go to use firefox those quicktime things are in spots and blocking me from clicking things and wont show the Flash stuff i cant figure out how to get rid of them. HELP PLEASE