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Try to experiment with Vsync options in nVidia Control Panel or Catalyst Control Center (depends on your graphics).

Example of my nVidia CP settings below.
Attachments:
So change it to ON.
TBH: For me game works fine so I can't be sure if it is due to bad vertical synchronization, but those lines are usually caused by Vsync option off. It's just a guess. What (monitor) refresh rate do you have?
Post edited April 05, 2013 by aMoosingOne