There are numerous possible causes for that error message.

The first thing to try is repairing the Office installation (via Windows Control Panel > Programs > Programs & Features > Microsoft Office (version) > Change > Repair).

You might also run the System File Checker, via:


sfc /scannow
as an Administrator from a Command prompt to validate your system files.

If that doesn't correct the problem, it might be caused by a faulty Addin. In that case, try stating Word in Safe Mode (i.e. hold down the Ctrl key while starting Word). If that corrects the problem, the issue is due to a faulty Office addin. Re-start Word normally, then disable all Addins. Log out then log in again and re-start Word normally. If the problem disappears, it was due to a faulty Addin. Re-enable one Addin, then log out, log in again and re-start Word normally. If the problem doesn't occur, re-enable another Addin. Keep doing this until the problem recurs; when it does, the last-enabled addin is the likely culprit. Permanently disable that Addin or replace it with the latest version.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]