Product Firefox Release Channel release Version 80.0.1 Build ID 20200831163820 (2020-08-31) Buildhub data OS Windows 10 OS Version 10.0.19041

bp-dfccbfd4-e7e5-4830-9c22-9f21e0200925 Signature: RtlReportFatalFailure | trunc | RtlReportCriticalFailure | RtlReportFatalFailure | RtlInitializeSwapReference | RtlpGetModifiedProcessCookie | RtlInitializeSwapReference | RtlpReportHeapFailure | RtlpHeapHandleError | RtlInitializeSwapReference | RtlpH...

Crash Reason EXCEPTION_HEAP_CORRUPTION

https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix

https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

https://support.mozilla.org/en-US/kb/firefox-takes-long-time-start-up

https://support.mozilla.org/en-US/kb/quick-fixes-if-your-firefox-slows-down

MemTest LAST UPDATED : 12/04/2020 Could you please run a tool from http://memtest.org/ in order to check the integrity of your RAM?

You will need a thumb or disk drive to install it on.

Do you let Windows handle the page file or did you set a fixed size ? If you use a fixed size for the page file then try the former and let Windows handle the page file.

Thank you FredMcD Unfortunately Memtest fails booting up from an USB key. But I have no indication whatsoever of a RAM fault: everything works fine. Windows manages paging file size. I followed several of the suggested checks where applicable (installed all optional driver updates, gave all permissions to Firefox under Windows firewall, disabled all extensions, disabled hardware acceleration) Disinstalled Firefox again, cleared all files related to Firefox, reinstalled again. Behavior is basically same as yesterday. Firefox NEVER starts normally, I get Crash reporter immediately. It only starts with shift-click in protected mode, and even there it sometimes crashes (with Crash reporter) after a while, even if I do nothing. When it happens to stay up in protected mode without crashing, when I close its window to exit I often get Crash reporter anyways. Here are some about:crash reports bp-0f863380-7a52-44c6-a56e-875670200926 bp-178c64ae-12c7-4f20-b16e-87f240200926 bp-e3018d1b-1146-434e-986c-25b550200926 bp-7fc16841-459e-4231-bdb4-ce7c60200926 bp-939bb8dc-650d-4dce-9a80-eba690200926 637a4126-19bf-4471-af68-acf4947aae71 the first looks quite interesting

Thank you FredMcD Unfortunately Memtest failed to boot from USB key. But RAM seems fine, everything but Firefox works ok. I again disinstalled Firefox and reinstalled after cleaning all Mozilla files and folders. I tried all applicable suggestions (installed optional driver updates, disabled all extensions, disabled hardware acceleration). Firefox keeps behaving as yesterday. It NEVER starts, goes to Crash-reports immediately. In only starts with shift-click in protected mode. When started in protected mode, randomly it crashes after a while (even if I do nothing) or it stays on. When it stays on, and I decide to close it and exit, randomly it goes to Crash-reporter. Here are some about:crash reports (the first one looks intriguing). bp-0f863380-7a52-44c6-a56e-875670200926 bp-178c64ae-12c7-4f20-b16e-87f240200926 bp-e3018d1b-1146-434e-986c-25b550200926 bp-7fc16841-459e-4231-bdb4-ce7c60200926 bp-939bb8dc-650d-4dce-9a80-eba690200926 bp-c016f34c-5e98-408c-a5ae-166e60200926 Thank you

thanks, the crashes are likely caused by the UltraMon multi-display software on your system that's hooking into the browser process - we've seen some similar stability issues with it in the past, so i think it would be best if you can uninstall/disable it...

Thank you Philipp what you say makes sense but, why Firefox started crashing suddenly a few days ago? Neither Firefox nor Ultramon was updated for months (Ultramon is unsupported and static since years)

firefox received an update to version 81 last week...