I have the same problem on my desktop PC. I've been running FF for years and very happily - that is, until the latest update from 72.0.2 to 73. After that update, FF 73 was not functioning. All I got was the toolbar. I lost bookmarks and my search engine. I could also not use Options. I tried uninstalling and reinstalling and all the usual tricks, but nothing worked. All I could do was use Windows 10 system restore to get FF 72 back. I even tried updating again, and the same thing happened. On my 2 laptops running W10 I had no problem. I hope this problem can be fixed soon. In the meantime, I'm not updating FF until a new update is released, hopefully with a fix for this problem.

NOTE: If you use the system restore trick to get back to 72.0.2, be sure to disconnect your Internet cable or wi-fi. If you don't, you won't have time to go into the 72.0.2 options to undo automatic update.

Hi matthewtgorman88, did this start with your installation of Firefox 73.0 yesterday? In other words, was Firefox 72.0.2 working normally?

Your crash report references a bug report about a conflict with a program named 0patch. Could you check this article:

https://0patch.zendesk.com/hc/en-us/articles/360011227079-Mozilla-Firefox-73-can-crash-upon-launching-when-0patch-Agent-is-installed

Hi zanotti1, your Firefox 73 had a different issue where the main browser process could launch but "child" processes were blocked from running. There is a patch in testing for that problem and it could come in a 73.0.1 update next week (I don't know the exact timing).

In the meantime, the primary cause of that problem for Windows 10 users is the following, although there may be other causes:

Compatibility Mode Problem in Firefox 73

Could you double-check that your regular installation of Firefox is not set to run in backwards compatibility mode? Here's how:

Find the icon you use to start Firefox, and either:

• Right-click a desktop shortcut, then click Properties
• Right-click a Firefox icon pinned to the Taskbar then right-click Mozilla Firefox, then click Properties

You should clear all the boxes on the Compatibility tab for best results (giant screenshot below).

Any difference the next time you start Firefox?

Thanks jscher2000 for your kind attention to this and your suggestions.

I'm currently running 72.0.2. I did as you advised. Yes, Compatibility mode for Windows 8 was checked and I unchecked it (I'm running W10, don't forget). If I understand correctly, you're suggesting that I go ahead and update to FF 73 and then run the Windows 10 compatibility check on that new version. Is that correct? If so, this will presumably fix the problem until the patch comes out next week (hopefully). Unfortunately, if that temporary fix doesn't work, I'll have to roll back the system restore again. Tedious and time-consuming. Might it not be simpler to just wait for the patch? How sure are you that the Compatibility trick will work on 73 in my case? Pragmatically-speaking, 72.0.2 is working fine for the time being. Your call.

Thanks very much for your help. Much appreciated.

Hi zanotti1, no rush to update, but please ignore any suggestion from Windows to use backwards compatibility settings for Firefox. I think that configuration doesn't get much testing and is likely to be more problematic.

Hi again, jscher2000.

To follow up, what is the best and safest way to find out when the fix is available. I presume it will be 73.0.1. I don't want to run the risk of unintentionally updating to 73.0 and the problem starting all over again.

Many thanks.

Hi zanotti1, I suspect someone will update these threads when an update is available, but you also could keep an eye on the "Releases" page.

https://www.mozilla.org/firefox/releases/

Many thanks for this. It's just what I need. I'm sure it's helpful to others too. I'll keep you posted on what happens after the 73.0.1 release.

Hi zanotti1:

Firefox 73.0.1 was released today. I believe it fixes your problem.

Please give it a try.

Cheers!

...Roland

Yes, it did fix the problem, Roland! Many thanks to you and jscher2000 and Firefox for working this issue out. Problem solved!