1. At the top of the Firefox windowOn the menu bar, click the Tools menu and then select Add-ons. The Add-ons dialog appears.
  2. Select the Extensions panel. The list of installed extensions is displayed.
  3. Select SwitchProxy Tool.
  4. Click Disable.
  5. From the menu at the top of the Firefox windowbar, select FileFirefox and then select the ExitQuit FirefoxQuit menu item.
  6. Restart Firefox. Open several new windows to see if Firefox no longer hangs.