Exception in mc3.dll / mc3d.dllARX Command Error - AutoCAD 2016 & other versions

[Azmeera.M]

If you tried opening a file or sometimes while working in your AutoCAD, the program crashes with an unhandled exception error in the specific mc3.dll or mc3d.dll files (see image above) with the message:

Exception in mc3.dll / mc3d.dll ARX Command
Unhandled Exception C0000005 (Access Violation Reading 0x0000) at address B91B60F4h

Cause:

Damaged WHITELIST.XML file, specifically affecting AutoCAD Architecture 2016 and AutoCAD MEP 2016.

Solution for AutoCAD Architecture 2016 & AutoCAD MEP 2016:
To fix the crash for the AutoCAD Architecture 2016 and AutoCAD MEP 2016:

1. Exit all Autodesk programs 
   
   
2. Navigate to the folder:
   
   AutoCAD Architecture 2016:
   C:\Users\<user>\AppData\Roaming\Autodesk\ARCHDESK\2016\{5783F2D7-F004-0409-2102- 0060B0CE6BBA}\7.8.44.0\MC3
   
   AutoCAD MEP 2016:
   C:\Users\<user>\AppData\Roaming\Autodesk\BLDSYS\2016\{5783F2D7-F006-0409-2102-0060B0CE6BBA}\7.8.44.0\MC3
   
   
3. Delete the WHITELIST.XML file
   Note: The numbered build folder containing the XML file (the folder just before MC3) varies, based on whether or not any service packs are installed. If the XML file does not appear in the build folders listed above, check the other numbered build folders for the XML file.
   
   
   
   
4. Restart your computer.

Important: Launching AutoCAD Architecture 2016 or AutoCAD MEP 2016 will download a corrected WHITELIST.XML file, as long as Desktop Analytics is enabled.  

Solution for other versions of AutoCAD including AutoCAD LT:
You can bypass the functionality that's causing the crash by doing the following:

First:

1. Go to Help > Desktop Analytics (or type DESKTOPANALYTICS on the command line).
2. Deselect the "Yes, I would like to contribute to this program." option.
3. Click OK.

Next:

1. Go to Help > Customer Involvement Program (or type CUSTOMERINVOLVEMENTPROGRAM on the command line).
2. Select "No, I do not want to join the program at this time."
3. Click OK.
4. Restart the program.

If AutoCAD crashes before you can disable the Desktop Analytics and CIP options, you can make an edit in the registry:

1. Close all instances of AutoCAD.
2. Press WINDOWS-R on the keyboard to bring up the Run window, enter REGEDIT and click OK.
3. Navigate to and select the following registry folder:
   HKEY_CURRENT_USER/software/Autodesk/MC3
4. On the right pane of the window, double-click ADAOptIn.
5. Change the value to 0 (zero).
6. Click OK and close the Registry Editor.

Alternatively, if you have an older version of AutoCAD installed, disabling the Desktop Analytics and CIP options within it should apply to version 2016 too.

Warning!
Problems caused by improperly editing the Windows registry could render your computer operating system unusable. Microsoft provides a wealth of critical information that you need to know about the registry in the Microsoft Knowledge Base. Use the Microsoft Registry Editor only at your own risk and only after backing up the registry as outlined for your operating system in the Microsoft article How to back up and restore the registry in Windows and in the related solution How to backup the system registry. Additional information about the registry is also contained in the Help topics in the Microsoft Registry Editor.

Related resource:
Visit our forum page dedicated to this topic
Autodesk Knowledge Network

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