Normally I'd be inclined to say it was the gfx card as the artefacts on the monitor appear on certain backgrounds and will even follow certain items around on the screen (ie using a freecam in a 3d game certain walls will have a sparkly blue to them)... However even running games at the same resolution I can't replicate issue on second monitor. The monitor is fairly old - bout 4 years and the graphics card is about 2. (Yeah I know replace them both...... lets not go there)
I've seen a fried laptop gfx card in action before and it doesn't seem the same. I've also run a gfx card memory tester and it came back ok.
I'll probably test it in the weekend with my work laptop and see what happens, but thought I ask if anyone had see this behaviour before.