MathType 6.9b, Word 2016, and McAfee products

If you can’t edit formulas with MathType and you receive a cryptic error message:

Word cannot open the document: user does not have access privileges

In Norwegian this becomes:

Word kan ikke åpne dokumentet. Brukeren har ikke tilgangsrettigheter.

Check to see if any McAfee products are installed. Remove them, reboot the computer, and see if the problem has gone away.