These couple days, when I start ubuntu, and after about 15 min to 1 hour, the colors of the Panel icons (time, username, language, network...etc) change their color and become white, and the Close, Maximize and Minimize buttons don't work in all windows.
Also, I see that the three buttons (Close/Maximize/Minimize) show in desktop as well (It used to show "Ubuntu desktop").
Although it's not big deal, but it's bothering, so what might be the problem?
Thank you.