There is more than one version of the Flash Player, you need to double-check that you have installed the version of Flash Player that Firefox uses. Firefox and IE use different versions of the Flash Player, and Chrome has its own version of the Flash Player built in.

A quick way to find out if you have the version used by Firefox is to visit the following link using Firefox - http://www.adobe.com/software/flash/about/

If it shows that Flash is not installed, using Firefox you can install it from http://get.adobe.com/flashplayer/ or use the manual installers, for details see http://kb2.adobe.com/cps/191/tn_19166.html#main_ManualInstaller

I had this problem for a while; and, I finally determined that the new Flashplayer was not installing because its error message was actually using flashplayer to inform me that it wouldn't work. Stupid Yup; but, when I opened up the Flashplayer app and hit the "Quit" (whatever) button; it finally installed and ended my problems...... Now if'n anybody knows why "Download Them All" stalls @ 25% --- I'ld be a happy camper 2. G............