I often can't erase and must start whatever I'm doing over again in another window.
I've talked to Apple and we reinstalled Firefox. It worked for about a minute (until I'd hung up) and went back to the same problem. Often (as in this email, possibly) I can't erase if I make a mistake. Actually, I just was able to. But in the google bar or in an email it often happens.
Re: I often can't erase and must start whatever I'm doing over again in another window.
The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information.
Note: This will cause you to lose any Extensions, Open websites, and some Preferences.
To Reset Firefox do the following:
Go to Firefox > Help > Troubleshooting Information.
Click the "Reset Firefox" button.
Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
Firefox will open with all factory defaults applied.