A similar question has been asked earlier Couldn't load XPCOM.

First check if you use any form of identity protection, because by reading the Q&A above this seemed to be the problem (in this case the anti-virus responsible was Webroot Secure Anywhere).

If identity protection doesn't seem to be the problem, try to re-install Firefox.

Hopefully this will help you solve your problem.

Do a clean reinstall and delete the Firefox program before (re)installing a fresh copy of the current Firefox release.

• Download the full Firefox installer and save the file to the desktop
  https://www.mozilla.org/en-US/firefox/all.html

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

• Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program before installing that newly downloaded copy of the Firefox installer.

• (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
• (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

• It is important to delete the Firefox program to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall