This happens on ONE Windows 7 PC. It does not happen on any other Windows 7 PCs. The problem appears with Winbox 2.2.13 and 2.2.16. It doesn’t happen on other Windows 7 PCs with the same Winbox connecting to the same router.
When I resize an internal window I get this gray fill:
Maximizing the torch window (or whatever) will fix this and as you can see, updating values and the aggregate traffic (for torch) overwrites the gray fill.
Has anyone seen this? Solved it? Any ideas on solutions?
you have blurred out the most important part of the image. my guess is, that you have installed some addon, which adds a button next to the windows minimise button. I have seen this before, so uninstall any windows addons which affect window behavior.
That gray is not blurred, that is what it looks like. I only blurred where there were numbers and figures.
I don’t have any additional window buttons and I can’t think of any related window changing applications. I just went through my add/remove programs list and found nothing that I could imagine to be related.
EDIT: It was DisplayFusion
Q.E.D. 
Thank you so much! “Actual Multiple Monitor” also causes same problem. Stopping it fixed the issue.