Pollock's right, it's because your screen is refreshing at 60Hz. (Can't believe you don't get a headache looking at the screen.
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You need to check the information on your monitor and then turn up the refresh rate.
Refresh rate can be changed at: right click desktop -> properties -> settings tab -> advanced button -> adapter tab -> refresh rate selector pull down menu.
Be aware you *might* damage your monitor if you pick a refresh rate that is too fast for it to handle. Usually windows will switch it back in time, but that's why I say to check the monitor specs.
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bloom25
(Formerly of the)
THUNDERBIRDS