Visual Bug hapenning.

When im in game, everything is fine till a non-predefined time were a colored box start to flicker on the top screen where the timer display use to be. That box has no precise color. It could be blue sometime it is 5 line of different color forming the box or can even be pink. Well i dont know what is the cause of this and its quite pretty annoying. Its been a while since im playing with that. Note that Alt-Tab out and in remove it for a little while till it comes back. I've tried to lower my graphic and else but this doesnt seem to be the solution.

Im playing on a 2 years old computer AlienWare aurora r4 with 2 grapic card put into crossfire AMD Radeon R9 200 Series I can play everything fine at max fps/graphic without any problem. Onli League of legends do that kind of thing.

https://pbs.twimg.com/media/Cf0xkv-UsAAWeHQ.jpg

You can see the square (now purple-ish) at the top. The square flicker a lot being translucide. Note that i use 2 screen. Sry for the quality of the picture. Had to take it with my phone since print screen or play.tv didnt recorded the box at all.(Also forgot to remove the flash before taking the shot.)