Let me report that I found another issue I had not regarded so much as I should... I use Evolution through Alltray (so as to dock the program at the notification area instead of minimizing to the window list). Whenever I run Evolution through it, the problem exists, when I run Evolution "clearly", there is no problem. The theme has nothing to do with it. Simply I quited the program when I changed the theme and ran it again without Alltray...
It turns out that it was a matter of Alltray, though it still looks strange to me.
Let me report that I found another issue I had not regarded so much as I should... I use Evolution through Alltray (so as to dock the program at the notification area instead of minimizing to the window list). Whenever I run Evolution through it, the problem exists, when I run Evolution "clearly", there is no problem. The theme has nothing to do with it. Simply I quited the program when I changed the theme and ran it again without Alltray...
It turns out that it was a matter of Alltray, though it still looks strange to me.