Dark Horizontal Lines on Monitor During Games...PLEASE help

I just ordered two Acer LCD monitors one a 22 inch and a 24 (http://www.newegg.com/Product/Product.aspx?Item=N82E16824009154). When they are both being used on the desktop they look perfectly normal; however, on either monitor when I play a game dark horizontal lines (usually grey in color) run through the monitor. I am really getting desperate, ive sinked more than 800$ at this point and neweegg has a strict no return policy for monitors (unless you want to exchange for a monitor of the same type). I contacted Acer customer service and it was just plain horrible, I could literally here the lady flipping through pages to try and find a solution. Anyone have any ideas

EDIT: And im certain its neither of the video cards on either computer, because I hooked up my other Samsung 24 inch and it worked fine during games with no horizontal lines.

Resolutions on both acre monitors are native, and likewise for refreshrates