spreadsheets scrolling right

Opening a spreadsheet causes it to scroll to the right endlessly, making it impossible to access or enter data. The same happens with a new blank spreadsheet. I can open the same spreadsheets on another computer over the network without a problem. I have re-booted the computer, deleted and re-installed Calc, updated my kernel, - any suggestions as to what I should try next? Is there a hidden file that I should delete?
Modern computer, Linux Mint 18.3, Kernel 4.13.0-39, Cinnamon 3.6.7,

Have you tested with other keyboard?

Yes, different keyboard, different mouse.

This cannot be caused by Calc; I installed Gnumeric and still had the same problem.