REndering artifact with Intel HD graphics, on

I get a weird blue line when I jungle in summoner's RIft. It starts from my HUD and draws across the screen. It only seems to happen when I fight jungle monsters. And it didn't happen prior to this new map... I don't have a gpu, just Intel HD and an i5 3570k, which runs it really well. I'll try to post a screenie when it happens, as it is quite random. I tried reinstalling the game, still happens.