I've posted over on Support, but it looks like the nice developers are too busy to drop in.
I'm hoping to solve the trouble on my own before having to bother them with an email describing the problem and including my DXDIAG and all the steps I've already tried!
When you look at the bottom of your Options menu in Super Granny 4, do you see "Version: SLG 1.000"?
Thank you very much for helping me out on this -- I love playing the user-made levels when I need to destress, but it's nearly impossible when Granny suddenly ignores the "Dig" button!