Have you tried an uninstall then install yet of the current version?
If this is still the norm after that. It may be time to post a dxdiag to see what your vid card and drivers are. The gunsight mask is a window within a window, and I can see your default.bmp is being rendered but, not 256x256. More like 256x64.
Another test would be to make a copy of the default.bmp. Erase the current gunsight ring and dot. Make sure the background is black. Then dead center place a large red dot and save. Then see if that dot will render in the gunsight mask and where. Post up that picture for us.
Better yet and a lot of trouble. In red draw a line grid along with the center dot of say 1\8 divisions in 5 pixel wide lines. Then see how the dot and grid are rendered along with a picture posted back here.
But first, uninstall and reinstall completely.