Re: When I have more then one tab, the second or third tab will suddenly close and reopen as a new window., how do I fix this? Happens at random times.
Current Firefox versions have a feature called tear-off tabs.
You can detach a tab from the current window and open it in a new window by dragging a tab in the browser window.
You can drag that tab back to the tab bar in the original window to undo that detaching.