Dear All: Suddenly FF starts but shows only a new tab without any content. I can fill in a URL but no reaction. Settings doesn't open. Close tab through X Restart FF. no new tab but message: ''FF is already running but is not responding. The old FF process must be closed to open in a new window.'' Click to close. a new empty tab pops up without starting FF manually. Close through X Restart brings the same message as above - no window. Have to end FF in Task Manager. Uninstalled and reinstalled three times - no change. I'm using Windows 10 and Avast One, Firewall checked - is open for FF. I appreciate your comments and help. Best wishes Henning