The 60 FPS only is what V-Sync is, it limits the framerate of your game to match the refresh rate of your monitor. The reason for this? Well it can deliver a more consistent feel to some games, some people do it so their card isn't running 100% all the time for a situation like yours where its breaking a few hundred FPS.
As to why you're see black lines all over I'm not sure. If it only occurs when you're playing Starcraft 2 it's more likely not your monitor but some weird setting or glitch in drivers/game.