I decided to revisit Half Life 2 and some other source engine games (Black Mesa Source is out!) and have immediately noticed a stutter that happens every half second (with vsync enabled). I have monitored the FPS with the Precision software and it shows a steady line at 60. I have also tried with adaptive vync without any success =/ The only way I have found is to disable any kind of vsync and have screen-tearing instead with a high FPS.. I have also tried the new 306.23 nvidia drivers (and previous) with the same outcome. Anyone else have the same problem with the 680's and source engine games? Could it be SLI? Don't really know how to solve this. Doesn't happen in any other game engines that I have experienced, eg BF3.