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Library not registered error when Word starts

You start Word, and instead of being able to start work, you get this pretty frightening error message.

A client reported the following error when starting MS Word - this is the time that the apps Formatting ribbon loads and it's checking a number of MS Excel files in the background.

"Unable to cast COM object of type 'System_ComObject' to interface type 'Microsoft.Office.Interop,Excel.Application'. This operation failed because the QueryInterface call on the component for the interface with IID '{000208D5-000-0000-C000-000000000046}' failed due to the following error: Library not registered. (Excelption from HRESULT: 0x8002801D (TYPE_E_LIBNOTREGISTERED))."

Pretty awful message, and must admit in confused me initially. apps Formatting had been working, and the client thought they might have done a Windows update at some point.

Hmmm.  I reinstalled. Still had the message when we re-started Word, even after a reboot.  Grrr.

I looked at the other MS Word COM addins he had loaded - he had a few. I disabled them all except for appsEngineV2 (which is the apps Formatting/SmartDoc/WorkSmart addin).

Restarted Word, and no error.

I asked him whether he needed them all, which was only the Outlook Business Contacts or something like that.  We ticked that one, and restarted; still ok.

We didn't work out which one was creating the conflict; he was going to do that on the way back to NZ but hasn't reported in yet.

If you get this error, and you work out which Addin is causing the conflict on your PC please report it to the Helpdesk ( so I can post a list of problematic addins, and maybe even contact the developer - they may be disabling a registered Library without needing to.



1. Go to MS Word > Options > Customize Ribbon, and tick the Developer ribbon.  Click OK

(Note, in Word 2007, the option to display the Developer tab is under Popular).

2. Click on Developer tab > and look for "COM Addins"

3. Click on the COM Addin button. The Addins list is displayed.

If you are experiencing this Library Not Registered error, de-select all addins except appsEngineV2.

Click OK and restart Word.

Next re-introduce each addin that you need, and after ticking each one, restart Word.  The Library Not Registered error will display again when you re-instate the addin that has the conflict.

If you require this addin, you might need to disable it, and just enable it when you need it.  Or disable appsEngineV2 unless you need it. 

Let us know what you find! 

If you still experience an error when starting MS Word, disable the appsEngineV2 addin as well, and restart Word.

If you still experience an error, it might be because you have addins in Excel that are causing a conflict.  You will need to investigate which of your Excel addins might be causing the problem by disabling all Excel addins.  Once disabled, you should be able to re-enable the appsEngineV2 addin and run it without problems.

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