Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

firefox-49.0a2.en-US.win32 fails with "Can't load XPCOM" on Windows 10 Insider Preview build 14372.

more options

Firefox Developer Edition 49.0.a2 fails to load on Windows 10 Pro Insider Preview build 14372 with the dreaded "Can't load XPCOM" error. I have tried reinstalling, uninstalling/reinstalling without success. The standard version of Firefox installed using the "Firefox Setup Stub 47.0.exe" does work correctly on this Windows Preview build however, So I will use that for now until there is a fix.

Firefox Developer Edition 49.0.a2 fails to load on Windows 10 Pro Insider Preview build 14372 with the dreaded "Can't load XPCOM" error. I have tried reinstalling, uninstalling/reinstalling without success. The standard version of Firefox installed using the "Firefox Setup Stub 47.0.exe" does work correctly on this Windows Preview build however, So I will use that for now until there is a fix.

Asịsa ahọpụtara

Turns out this is not a Windows 10/Firefox Developer Edition Issue. It's instead a problem with Cylance <https://www.cylance.com> determining that some of Firefox Developer Edition's .DLL files are evil (or could be used for evil purposes)

Specifically it Quarantined the files: c:\program files (x86)\firefos\developer\edition\mozavutil.dll C:\Program Files (x86)\Firefox Developer Edition\lbplibs.dll

Cylance does not use signatures for finding malware, but instead uses heuristics to figure out what the code does (or is capable of) and unmercifully prevents all access to suspect files. To my knowledge Cylance (the company) does not provide a white-list of files or programs either. Local administrators can locally white-list files on a per-computer or per-site basis. As an equal opportunity hater, Cylance is also quarantining several of the SysInternals Suite of programs, as well as my Cygwin shell and compilers, too. That's why I'm on the Insider preview, for the new Ubuntu bash shell.

Gụọ azịza a na nghọta 👍 0

All Replies (4)

more options

hi ckloiber, are you using any sandboxing software on that system or is this happening on a pc with particularly old hardware?

more options

No, this is on the Bare Metal. The hardware is an HP Compaq Pro 6300 (Intel I5-3470)

more options

Asịsa Ahọpụtara

Turns out this is not a Windows 10/Firefox Developer Edition Issue. It's instead a problem with Cylance <https://www.cylance.com> determining that some of Firefox Developer Edition's .DLL files are evil (or could be used for evil purposes)

Specifically it Quarantined the files: c:\program files (x86)\firefos\developer\edition\mozavutil.dll C:\Program Files (x86)\Firefox Developer Edition\lbplibs.dll

Cylance does not use signatures for finding malware, but instead uses heuristics to figure out what the code does (or is capable of) and unmercifully prevents all access to suspect files. To my knowledge Cylance (the company) does not provide a white-list of files or programs either. Local administrators can locally white-list files on a per-computer or per-site basis. As an equal opportunity hater, Cylance is also quarantining several of the SysInternals Suite of programs, as well as my Cygwin shell and compilers, too. That's why I'm on the Insider preview, for the new Ubuntu bash shell.

more options

thanks for the update!