HELP! Guidelines have stopped working!

I know that guidelines were working a couple of weeks ago; haven't needed them more recently.  Today, however, when I drag from the ruler it shows a guideline but when I stop dragging it disappears!  I can't get any to set, horizontal or vertical.  When I try to access any guideline settings via a menu option or docker, CorelDraw X7 crashes.  

What in the world would have changed on my Windows 10 Pro system to cause this? 

(Dell Inspiron 5749, Windows version 10.0.15063, x64, 2.40GHz, 8 GB RAM)

Thanks!

Lisa in The Lowcountry