Why does this happen?! (see below image)

It only occurs when rendering magical effects like wards, or the circle in the image below, or the eye of magnus' effects, etc

It's driving me insane. GPU is a gtx 560 ti



[img]http://i49.tinypic.com/elkjc.jpg[/img]

Looks like screen tearing caused by disabling the game's vsync to me.