If after updating your Mozilla Firefox and suddenly you have problem opening or accessing Firefox browser.
You can see the remark at the left hand bottom of the screen which says: "waiting to download Firefox." The screen is blank and you can see the spinning arrow icon.
Then it is your PROXY settings problem:
1) The proxy server is refusing connections
2) Unable to find the proxy server
This is how to check your proxy settings:
1. Click Tools menu then click Options.
2. Select the Advanced panel.
3, Select the Network tab.
4. In the Connection section, click Settings...
5. Change your proxy settings. If you don't connect to the Internet through a proxy (or don't know whether you connect through a proxy), select No Proxy.
6. Close the Connection Settings window.
7. Click OK to close the Options window
