I did a clean re-install and now I get from time to time this blue square glitch that appear always in the top right corner of my screen and seems to come from shadows. it last only a frame or so, very short but it bothers

E8400, 560 ti, 4 gb ram.

Screenshot, please. It'd help with us knowing what you're talking about.

it seems my htc home 2 clock/whether gadget interfered. as soon as I closed it, my blue square glich dissapeard. weir as until yesterday, I haven`t had this issue. anyway, it`s solved.