Same issue here.
With fresh install of Fences 3.0.9.11, up to date Win10.
Multiple Monitor setup, made clean install of latest Nvidia graphics drivers as suggested above.
Problem persists.

In this picture, you can see one of three (or more) effects:
- icons leave black artifacts after mouseover
- background goes full black
- icons leave background color artifacts on wrongly black background (even all fences/icons were hidden by double click!)
Interestingly, the save dialog for saving the screenshot to disc instantly recovered the background.
This issue is annoying and makes me think I should have tested before buying.