Something wrong with my CS 4

 Hello, I'm having a problem which annoyed me, so recently I just installed adobe photoshop CS4, I dont khnow why but there's something wrong with me photoshop, I lready re-installed but the problem wont go away, and I'm really confused. 



see that line thing, I dont understand why is it there, and it will only disappear if I zoom it into 200%
So, can anybody help me please ? thank you before