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TechNote #135: Last modified: 11/04/2016

Microsoft Word: AutoExecCLS or UIRibbonCLS Error

The information in this document applies to:

  • MathType 6.x (Windows)
  • Microsoft Word 2003 and later


When starting Microsoft Word, there are occasions where one of the following error messages will be displayed:

"MathType has detected an error in AutoExecCLS. Error running cmd=NoDirectCall_Main mod=AutoExecCLS in RunMTDLL Command: Method 'Path' of object 'Addin' failed. Please save your document and report this to Design Science Technical Support."

"MathType has detected an error in UIRibbonCLS.Error running cmd=NoDIrectCall_OnInsertInlineEqn mod=UIRibbonCls in RunMTDLLCommand: Object doesn't support this property or method. Please save your document and report this error to Design Science Technical Support."


If Microsoft Word was running when your computer was restarted after a Microsoft Auto-update, this error can occasionally present itself the next time you start Word. For more information see the The error message indicates a problem with the Microsoft Word Toolbar/Ribbon. Below are instructions for resetting the Word Toolbar/Ribbon.


 Use the following instructions to "reset" the Word Toolbar/Ribbon.

  1. Exit all Office programs.
  2. Click Start
  3. Type regedit in the Start Search box, and then press ENTER.
  4. If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
  5. Locate the following registry subkey:
    • HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Word\Data (Where "xx" corresponds to your version of Office)
  6. Click Data, and then click Export on the File menu.
  7. Name the file Wddata.reg, and then save the file to the desktop.
  8. On the Edit menu, click Delete, and then click Yes.
  9. Exit Registry Editor.
  10. Restart Word.

If Word starts and works correctly, you have resolved the problem. The problem was a damaged Word Data registry key. You may have to change several settings to restore your favorite options in Word. You can now delete the exported key saved on the Desktop from item 7 above.

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