For the past year or so, I've been experiencing episodes of strange visual artifacts on my 30" ACD (GeForce 6800 Ultra 256 MB). These episodes are very intermittent and disappear without warning. I'd describe them as bright green, single pixel threads running throughout the display, tending (but not always) to follow along the edges of color boundaries. Forcing a refresh by dragging a window or launching an application will usually make them disappear, though they usually disappear after a minute or two on their own (they disappear all at once, I believe). Tonight I managed to grab my camera and snap a few pictures (screen capture does not show them). Sorry for the quality of the pics, but these should give an idea of what's going on. Is this a video card problem, an ACD problem, or something entirely different?