If the problem was an automatic border (I don't know if you ever confirmed or denied that), turning off the AutoFormat As You Type options will help. Click File tab | Options | Proofing | AutoCorrect Options | AutoFormat As You Type. For more, see the article I linked to previously.

Also, just to be clear, I don't work work for Microsoft, and neither does Paul.

__________________
Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional

Stefan, yes it was an automatic border. Thank you for being the one to actually help me by answering the question, and for the follow up. This happened when I was putting in lines like these __________ into a contract to be filled in later. I have later tried to duplicate the error in Word 2007, but I was not able. In my unprofessional opinion Word 2007 and before are far more “forgiving” than Word 2010.

Consider using table cells with fixed dimensions when you want to create simple form. Add and remove borders as desired.

As far as AutoFormat As You Type is concerned, the defaults remain unchanged since Word 97. If you used Word in a corporate environment, perhaps settings have seen modified by group policies...

__________________
Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional