I have the same problem as VncentV and PaulHowith with .doc & docx files that have passwords suddenly not opening in Word. The files open on an alternative machine running exact the same software (Office 2016 Windows 10) I have tried repairing Office twice but no improvement. I can create a file with a password on the "defective" machine and it does not open but opens perfectly normally on alternative machine? Any help gratefully received. Many thanks.