Then you have a config problem in FF. probably protected mode:
Disabling Protected Mode in Flash 11.3
To disable (or re-enable) Protected Mode in Flash 11.3 and above, use one of these methods:
- (Starting in Firefox 38) In the Firefox (Tools) menu, click "Add-ons -> Plugins -> Shockwave Flash Options (button)", clear the "Enable Adobe Flash protected mode" checkbox and restart the browser. (To re-enable Flash Protected Mode, re-check the checkbox.) [45]
- (Starting in Firefox 35 on Windows 7/Vista, Firefox 36 on Windows 8) Toggle the "dom.ipc.plugins.flash.disable-protected-mode" preference to "true" in about:config and restart the browser. (To re-enable Protected Mode, set the preference back to "false"). [46]. [47] [48]v
- Edit the Flash mms.cfg file
To disable Protected Mode, use a text editor to add the line
ProtectedMode=0 to the Flash "mms.cfg" file, located in one of these locations:
[49]
(Windows 32bit) C:\Windows\System32\Macromed\Flash
(Windows 64bit) C:\Windows\SysWOW64\Macromed\Flash
For example, on a Windows 7 64-bit system, open the
C:\Windows\SysWOW64\Macromed\Flash folder, copy the file "mms.cfg" to the desktop, open it in Notepad, add a new line
ProtectedMode=0 and then close Notepad, saving your changes. Next, go back to the
C:\Windows\SysWOW64\Macromed\Flash folder, rename the original file to "mms.cfgBAK" (to save it as a backup) and then drag and drop in the modified "mms.cfg" file from the desktop. To re-enable Flash Protected Mode, either restore a backup of the original mms.cfg file, if you saved one, or else re-edit the mms.cfg file to remove the
ProtectedMode=0 line you added. Updating Flash Player or installing a newer version does not automatically re-enable Protected Mode.
Flash - MozillaZine Knowledge Base
If you don't have 11.3 the procedure should be pretty much the same.