If you have different versions of MS-Office projects installed (e.g. Project 2016 and Excel 2013) on the same computer it will result in different versions of the MS-VSTO library being installed.

This is described in this Microsoft Developer Network (MSDN) blog:



"...So I rang the customer to discuss it further and it turned out that they installed Project 2010 to these boxes running Office 2007 that seemed to have added a newer automation class registry key for Excel and Word though even though it was not even installed.

Anyway, deleting the key HKCR\TypeLib\{00020813-0000-0000-C000-000000000046}\1.7 solved the issue for the customer.

Project, Excel, Word and Team Explorer work fine with that tiny little change

My learnings: “When in doubt, run process monitor.”...."

So, if you see this error, use the Windows Registry Editor (REGEDIT.EXE) and:

Remove the two keys for Excel:

  • HKCR\TypeLib\{00020813-0000-0000-C000-000000000046}\1.8
  • HKCR\TypeLib\{00020813-0000-0000-C000-000000000046}\1.9

Then remove the two keys for Word:

  • HKCR\TypeLib\{00020905-0000-0000-C000-000000000046}\8.6
  • HKCR\TypeLib\{00020905-0000-0000-C000-000000000046}\8.7

Then reinstall the MS-Office 2010+ add-in from our website, reboot and the issue will be resolved.  You should no longer receive the COM error: