Using Word is impossible as a box headed "Windows Security" keeps popping up

[Hambagashle]

When I try to go into an existing Word document, or to start a new one, this is made impossible because a box pops up. Its heading is "Windows Security". It says "connecting to office.microsoft.com". It asks me to enter my credentials i.e. User Name and Password. I enter these, and click OK but get nowhere. The box continues to pop up with the same request. Clicking on the cross, or on Cancel gets nowhere. I cannot close the Word document because of it. The only way out is to close down the computer. I am not getting this problem in any area other than Word. I can use my genealogy software OK, I can go online OK, I can read and print emails OK.