Dots from my video card

I just built a brand new pc with a evga eGeforce7900 GT video card and view sonic va1912wb wide screen digital/analog monitor.
When I run quake 4 after about 5 to 15 minuits I began to notice little different color dots in the screen and sometimes when I exit to game to windows, I notice windows is often affected with dis-coloration. What is the problem and how do I fix it?