When I maximize a window, my "X" and the minimize icon in the top-right corner of the window are replaced by small boxes of the same size. They look to be black with little green lines running horizontally through them. The restore icon is unchanged. If the window is not maximized, the icons are normal.
I had heard it may be a font issue, but since they work normally, I didn't think this was the case. I've scanned for parasites and viruses and found none. Any ideas?