При установке дополнения Flagfox FF выдает - "ошибка загрузки - 228", при том, что раньше на этой версии 3.6.6 это дополнение устанавливалось и работало.

Download Error -228
Disabled cache

This error message may be caused when the Firefox cache is disabled. To re-enable the Firefox cache:

    At the top of the Firefox window, click on the Firefox button (Tools menu in Windows XP) and then click OptionsOn the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select PreferencesAt the top of the Firefox window, click on the Tools menu and select Options...On the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select Preferences...
    Select the Advanced icon.
    Click on the Network tab.
    In the Cache section, the size of the cache must be at least 1 MB.

Other software

Sometimes, firewalls or spyware screeners may cause the Download Error -228 message. If you use the CA firewall, Windows Defender, or the resident option of Spybot S&D ("Teatimer" feature), you should temporarily disable the software to see if your system permits the add-on to install. For more information, see the documentation that came with your software.