Hi Michael, when you install Firefox, it creates a task to check for updates invisibly in the background. Maybe that is what is crashing? As a test, start Firefox, go to the Settings page, and uncheck the box for "When Firefox is not running" and see whether that helps. You also could go into the Windows Task Scheduler and disable the task, if changing the setting in Firefox isn't enough.

(I can't recall whether there is a setting to stop showing the crash reporter.)

I suspected something like that was going on. I think your suggestion will stop the Crash Reporter from popping up. One other question: For complicated reasons I'm using the Firefox 128 Portable Version, which is essentially the same as the regular installed version. However, even though it will give a notice that a newer version is available, it can't update itself in the Portable environment. To update I have to download a .PAF file and install it through the Portable Apps shell. Is there any way, maybe through the About:Config settings, to stop Firefox from checking for updates altogether? Or is that just not possible?

Firefox does not have an internal setting to block update checks. There are preferences that should space out the timing of either checks or reminders or both. I haven't experimented with those. Maybe I should right now since I am getting reminders about 128.0.2. If I can find them...

Let me know if you would what you find out concerning timing of checks or reminders. Setting those to maximum interval would be better than nothing.