AutoCAD/AutoCAD LT 2014, 2015 and 2016 on Windows 11 – random crashes on startup/open

Affecting all versions of AutoCAD and AutoCAD LT 2014, 2015 and 2016

Random shutdown on startup or opening of DWG files. AutoCAD may restart after a few attempts. You see errors like:

Unhandled Exception 4 (Access violation reading 0x0014) at address 70DC63A9h

Unhandled Exception 4 (Access violation reading 0x0014) at address 70DC63A9h







Additional error texts:

  • INTERNAL ERROR: Attempt to register class ‘AcViewNavigation’ twice
  • Error handler re-entered. Exiting now.

Issues are caused by the forced shutdown of AutoCAD components. You can fix the problem using the Longbow Converter App (you need version 12.61 or newer), steps to fix are as follows:

  1. Before installing the Converter App, make sure the files downloaded from our site are not blocked by Windows SmartScreen… Windows 11 is finicky, click the TLC zip first to make sure it’s fully selected then Right+click the file and select Properties. Be sure to check the Unblock checkbox as shown below and Click OK…
  2. Double click the zip file to open it and install the TLC application as normal. By the way, TLC stands for The Longbow Converter
  3. Start the Longbow Converter tool
    1. Select the 3nd tab named “Old AutoCAD Program Reviver
    2. Using the “” button
      1. pick the path to your acad.exe file (or for AutoCAD LT it’s acadlt.exe) 
        1. TIP: you can find the path by right-clicking the AutoCAD shortcut, clicking Properties and noting the ‘Target’ property e.g. C:\Program Files\Autodesk\AutoCAD 2016
    3. Click “Fix Old Program
  4. Now start AutoCAD. problem should now be solved. If not, please contact Longbow Support

Copyright 2024 (c) Longbow Software

AutoCAD LT 2015 on Windows 11 – FATAL ERROR: acismobj20.dbx

If you are running AutoCAD LT 2015 on Windows 11 and you receive this error…

FATAL ERROR: (0x7ffb71c40005) C:\Program Files\Autodesk\AutoCAD LT 2015\acismobj20.dbx

The issue is that you are running 64bit AutoCAD LT 2015 on Windows 11, this is an old version of AutoCAD which is easily affected by Windows Updates pushed by Microsoft. You need to install the 32bit version of AutoCAD LT 2015 instead as it is not as easily affected by the latest Windows components. To solve the problem, you must first uninstall your existing AutoCAD LT 2015 (do not install along side as it will not work) and then follow these instructions to install the 32bit version (which is much more reliable and actually runs faster)

Copyright 2023 (c) Longbow Software