This seems to be a very rare crash: 7 reports submitted, all today, possibly all yours.

Could you do this three-minute experiment:

Create a new Firefox profile

A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also should have completely fresh settings databases and a fresh cache folder.

Exit Firefox and start up in the Profile Manager by pasting the following into the Windows Run dialog or the system search box and pressing Enter:

firefox.exe -P

Don't delete anything here!

Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button, assign a name like TEST2016, and skip the option to relocate the profile folder. After creating the profile, select it and start Firefox in that profile.

Any improvement in stability?

When returning to the Profile Manager, you might be tempted to use the Delete Profile button. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.

thanks for the quick response; it's just been crashing out repeatedly as I've tried to re-open it, unfortunately. as I put in my original message though, I've already tried creating a new profile (still crashes immediately), among other troubleshooting steps after over an hour of googling.

my only suspicions are a recent windows 10 update, and recent NVidia and intel driver updates..

The crash occurs when Firefox is doing some kind of system lookup:

nsOSHelperAppService::OSProtocolHandlerExists() => calls shell32.dll

but the report doesn't mention what Firefox was looking up, for example, a file extension association? a content type association?

(Or at least, I don't see that information.)

Do you want to try SFC?

• http://windows.microsoft.com/en-us/windows-10/using-system-file-checker-in-windows-10
• http://answers.microsoft.com/en-us/windows/wiki/windows_10-update/system-file-check-sfc-scan-and-repair-system-files/bc609315-da1f-4775-812c-695b60477a93

tried sfc, which came back with an unable to repair error, so i finally just called it a day and restarted, and lo and behold, it opened up fine. i then closed it and copied everything from my old profile back into the default one, and everything seems peachy (it didn't crash)..soo it must've just had something to do with some files that were locked during a windows and/or nvidia update.

thanks again for your helpfulness and prompt responses, though! :)

If it happens again then try to reboot the computer.