Type '''about:config''' in the Location (address) bar and press the "Enter" key. When you see a warning, click '''I'll be careful, I promise!''' button. -> right-click somewhere, click '''New''' -> select '''String''' * name it '''xpinstall.enabled''' and set the value to '''True''' -> Close the '''about:config''' tab and then Restart Firefox. All the downloads should work now. If you delete this value some time later it still works. Check and tell if its working.