To fix the problem with the add-on, you need to disable the add-ons installed in your Mozilla Firefox web browser. You could also fix the problem due to Switch Proxy Tool by disabling it. You need to click the Tools menu and then select Add-ons, Select the Extensions panel, SwitchProxy Tool and then click disable. Your Mozilla Firefox may freeze or hang when you attempt to download or try to save images in your computer, this is caused due to the conflicts from the older files. You can easily fix this issue by clearing your download history.