An error message like XPCOM missing or about platform version or entry points not found can happen because of a failed Firefox update that left you with a mixture of old and updated files in the Firefox installation folder. This can happen in case security software was keeping a handle of some of the files in the Firefox program folder preventing Firefox from replacing all the files. You need to do a clean reinstall and remove the Firefox program folder to ensure that all files are replaced. You may have to disable security software temporarily in case the problem persists.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

Reinstall Firefox:

• https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems

I have the same question. No idea why, after years of updates that installed just fine, somehow this problem is occurring when nothing at all has changed. I keep seeing the same response being given over and over for reinstall and I've also seen a bunch of people saying that the reinstall did not fix the XPCOM error. I also have many passwords saved in Firefox and am looking for a way to save the files.