This is very strange indeed. While I can say that it is not caused by V-Sync directly, I also can not say what the cause is. I would guess that you have some 3rd party program that is causing this. This is probably not the most appropriate place for me to try and help you though, but I would suggest that you visit the forum for your video card manufacturer. They all have troubleshooting forums. Chances are that someone over there has encountered your issue and can help you with a solution.
drakkar123
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