10. April 2012 · 6 comments · Categories: TechBits · Tags:
unknown exception dialogAn unknown Exception may occur when launching Notepad++ ver. 5.9 (Unicode) or later. This problem appeared on a PC running WinXP SP3 32-bit, and according to information on Sourceforge, the issue may also apply to Vista, but not Win7. The cause appears to be four plugins that may be incompatible with the updated version of Scitilla.

The four plugins are:

  • AHKExternalLexer.dll
  • ExternalLexerKVS.dll
  • NppExternalLexers.dll
  • Oberon2LexerU.dll

Update (03/21/13): Many users experiencing the unknown exception issue with Notepad++ versions since 5.9 have resolved the problem by uninstalling the PreviewHTML.dll plugin instead (see comments).

Users can move the plugins one at a time into another folder within the “plugins” folder and relaunching the program to identify the plugin(s) responsible. In the case of the WinXP machine noted above with this problem, it was necessary to move only a single plugin, the NppExternalLexers.dll file, into another folder (e.g., disabled_plugins) to get Notepad++ to launch without error. The responsible plugin(s) can also be deleted or renamed.



  1. Timothy says:

    I was getting the “Unknown Ecxeption” error whenever closing a file, and for each open file when closing Notepad++. The comments referring to PreviewHTML.dll motivated me to uninstall the “Preview HTML” plugin, and then the problem went away. This was with Notepad 6.3 on Windows 7 SP1, and Preview HTML 1.2.1.

    Thanks for the tip!

  2. Alonso says:

    I´ve solved this problem by deleting the PreviewHTML.dll file from plugins folder. I think it could help anybody else with the same problem. that worked for me on Windows 7

  3. Jairito says:

    For my I delete the file PreviewHTML.dll and solved problem. Regards

  4. cyprus says:

    The Solution

    I’ve contacted the developer of the plugin and have sent some files for testing, but until then, here’s what I do to go about my merry way:

    If open, Close Notepad++ (it saves the settings upon closing)
    Open up the following folder (I’m on Windows 7):
    Delete the “Certificates.xml” file (I haven’t found any problems doing this, I just have to confirm invalid certificates again)
    Launch Notepad++

  5. admin_tb says:

    Did you try moving all the plugins to another folder? If that works, then move the plugins back in one at a time to see which is causing the issue. If you are going to uninstall the application, try using something like Revouninstaller which finds leftover files and registry entries – make sure to select and delete them all (leftover files and registry entries) before reinstalling Notepad++.

  6. Tony says:

    Hi! I have the same problem and I haven’t any of those four plugins installed.
    This started happening after I installed Notepad++ 6.1.1 and updated and installed some other plugins I can’t remember but I’m sure it wasn’t any of those four you mentioned.
    I have tried uninstalling and manually deleting the Notepad++ folder in the Program Files directory on Windows XP SP3. I also have cleaned the Registry with Ccleaner.
    It still does not work even after I reinstall, it still shows the Exception.

    What’s the problem? What should I do?


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