This bug has been occasionally showing up for me after the window for the champs/skins gets minimized. The one on the picture here was after I had selected a skin for Leona. After hovering my mouse over some of the spots for the Masteries and Summoner Spells, the borders and text will come back up, but not the pictures. The chat also gets severely skewed. The champ pictures on the sides also come back after a champ has been selected.