Old product, but still, it was so annoying, that I share it anyway. Maybe there are others stuck with VS2010 projects, or maybe later VS versions inhibit the same problem.
So: I use PhotoShop to edit the icon image for an app. To display the icon correctly on various backgrounds, I use a transparent background for the image. The icon file has to contain various resolutions from 16x16x bits to 96x96x24bits. Problem: I happened to change the images, but after that change, icon backgrounds became solid - transparency was lost. I tried changing the color that represented transparency, but nothing helped.