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Windows 7, FF 18.0.1 "NSSUTIL_EscapeSize couldn't find in dll nssutil3.dll" then "Could not load XPCOM" help please


The problem doesn't resolve, I then re-install 17.0.1 and works fine. Have tried this install with 18.0 and 18.0.1 same results

Modified by DGB

Additional System Details

Installed Plug-ins

  • Shockwave Flash 11.5 r502
  • Adobe PDF Plug-In For Firefox and Netscape 10.1.5
  • RealPlayer(tm) LiveConnect-Enabled Plug-In
  • RealPlayer Download Plugin
  • RealNetworks(tm) RealDownloader Chrome Background Extension Plug-In
  • RealNetworks(tm) RealDownloader PepperFlashVideoShim Plug-In
  • RealNetworks(tm) RealDownloader HTML5VideoShim Plug-In
  • RealDownloader Plugin
  • The QuickTime Plugin allows you to view a wide variety of multimedia content in Web pages. For more information, visit the QuickTime Web site.
  • RealNetworks(tm) RealPlayer Chrome Background Extension Plug-In
  • RealPlayer(tm) HTML5VideoShim Plug-In
  • Google Update
  • npFFApi
  • GEPlugin
  • 5.1.10411.0
  • Picasa plugin
  • Garmin Communicator Plug-In


  • User Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20100101 Firefox/17.0

More Information

Firefox 18 will not start so no trouble shooting info.

  • Top 10 Contributor
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10761 solutions 96861 answers

Do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

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

Download a fresh Firefox copy and save the file to the desktop.

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

  • Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

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

Your bookmarks and other profile 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.

Question owner

I followed the steps you have suggested, when I started FF 18.0.1 I still received the error "Could not load XPCOM". I reran this process to delete and remove FF 18, then ran Malwarebytes, no problems found, and cleaned the registry, then reinstalled FF 18. again the error "Could not load XPCOM" appeared again. I have reverted back to FF 17. Any other ideas to resolve this?


  • Top 10 Contributor
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10761 solutions 96861 answers

You did delete the Firefox program folder, because such issues are usually caused by a failed update to some files?

Question owner

Yes I deleted the Firefox program directory as per instructions. I think I will try a custom install and select a different directory for the program installed location.

Question owner

I just installed Firefox 18.0.1 in a different directory and Firefox now starts error free. Thanks for your support cor-el your input lead me to the solution,

  • Top 10 Contributor
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10761 solutions 96861 answers

You're welcome