Check to make sure that your resolution and frequency settings are right. Some displays also have an auto adjust feature, though usually offset happens when you're running at an odd resolution or frequency. There's also other causes but it's a decent place to start.
Bit of a note, refresh rates higher than your monitor supports can lead to a premature death of your monitor, though generally you will end up with a blank screen or a report of unsupported freqency or some games won't even let you chose it. Lower's fine but generally you'd like as high as you can go.
End note, no clue why I used frequency, couldn't remember probably.