I have this problem on my geforce 3 TI 200.
It is entirely related to electro-magnetic noise from inside my system as well as outside.
This is one reason monitor cables have ferrite cores on them.
there is no such EM protection from inside the case.
Considering I have 2 9000 RPM fans within 6 inches of the video card, I'm not surprised in the least.
It's not a design flaw, it's an environmental side-effect.