Firefox will not start.

[Miles_Umbrae]

For the past couple of weeks I've been unable to get Firefox to start.
When I try to start Firefox all I get is a blank window with nothing more than the Firefox-icon in the upper left corner and the Minimize, Maximize, Close buttons in the upper right corner and nothing else.
Trying to start Firefox from anywhere starts a Process in the Windows Task Manager, but no matter whichever method I use to try to close down Firefox neither the window nor the process closes down.
I can not access the menu-button and therefor can not get to the "Refresh Firefox" button or the Safe Mode.
Like most users I have multiple tabs open with things to get to "tomorrow", tabs that I do not want to lose if at all possible.
https://imgur.com/3bYmwMY

[malliz]

Did you re-boot your pc?

[Miles_Umbrae]

Did you re-boot your pc?

Second thing I tried...

[malliz]

There are ways to start firefox in safe mode without opening the program but it has to be closed to do.

You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.

[Miles_Umbrae]

There are ways to start firefox in safe mode without opening the program but it has to be closed to do.

You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.

I tried that, and everything else applicable found on support.mozilla.com
..everything except reinstalling Firefox, which I'm hesitant to do because of all the not yet bookmarked tabs that I do not want to lose...

[kerft]

The tabs should exist in the sessionstore files or sessionstore backup files. If you copy the whole %appdata%\mozilla folder to another drive or a USB key, you should be able to use files in the profiles in it to get the tabs back, either when Firefox works or by using this https://www.jeffersonscher.com/ffu/scrounger.html
So first, backup - either your profile, all of %appdata%\mozilla , or your whole computer.
Uninstalling and reinstalling Firefox should not affect your profile which has your data. Best process: uninstall, remove all shortcuts that are left behind. Set something else to default browser. Reinstall, set as default browser if you like.
If that does not work, what antivirus software do you use?

[Miles_Umbrae]

The tabs should exist in the sessionstore files or sessionstore backup files. If you copy the whole %appdata%\mozilla folder to another drive or a USB key, you should be able to use files in the profiles in it to get the tabs back, either when Firefox works or by using this https://www.jeffersonscher.com/ffu/scrounger.html
So first, backup - either your profile, all of %appdata%\mozilla , or your whole computer.
Uninstalling and reinstalling Firefox should not affect your profile which has your data. Best process: uninstall, remove all shortcuts that are left behind. Set something else to default browser. Reinstall, set as default browser if you like.
If that does not work, what antivirus software do you use?

I'm using Avast antivirus.

[TheVisitor]

I'm using Avast antivirus.

See here: https://support.mozilla.org/questions/1264440 Read the link for Moz Support. Avast is your problem.

[Miles_Umbrae]

I'm using Avast antivirus.

See here: https://support.mozilla.org/questions/1264440 Read the link for Moz Support. Avast is your problem.

From the conversation it sounds more like Firefox is the problem as it is the program that was changed and started to conflict with programs that was not updated. (Yes, it's nitpicking, but accuracy is important)
Furthermore, the only alternative to solve this conflict leaves me with having to choose between finding a new safe browser(and loosing all the tabs), or to leave the security of my computer to inferior anti-virus software...

[kerft]

Someone in these threads https://forum.avast.com/?topic=228355.0 https://support.mozilla.org/en-US/questions/1264440 said that a clean install of new firefox and new avast did work.
You can try posting in the avast forums.
You may be able to get your tabs using the scrounger linked above and put them into a new profile or any browser.

[Miles_Umbrae]

Someone in these threads https://forum.avast.com/?topic=228355.0 https://support.mozilla.org/en-US/questions/1264440 said that a clean install of new firefox and new avast did work.
You can try posting in the avast forums.
You may be able to get your tabs using the scrounger linked above and put them into a new profile or any browser.

OP in the Mozilla Support thread stated that a clean install did not work for them.