Most likely a video card issue. Try a new videocard?
Somewhat less likely: a monitor issue. But another monitor is so much easier to try than another videocard that it's best to do that first.
Kees
Over the past few days something came up when I'm playing games on steam... Some worse then others. There these clear dots that sometimes spaz out on the screen. Several decent sized dots everywhere.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic