Funny noise on external display

I have an external NEC LCD2180UX hooked up to my MBP 15" and since a few weeks funny lines started showing on the external display. The lines are bright green and magenta, 1 pixel high and ca. 200 pixels wide (though this might vary) and flicker very quickly, especially over dark image areas.
First I thought it was a faulty connection, so I tried a different adapter and DVI cable. Didn't help. So I thought changing the color profile might work, but it didn't. For some profiles the effect was worse than for others. Then I changed the resolution from the native 1600x1200 to a smaller resolution and voilá, all lines gone, no more flicker.
Still, I want my full resolution back! Does anyone know something about this? Is it a hardware defect? Software bug?

That's typical of DVI noise. The pixel clock can be quite high for legacy UXGA (1600 x 1200) timing. By legacy timing, I mean timing that has a generous blanking allotment as needed for a CRT-based display. But an LCD can work from a timing with much less blanking without any drawback. Unfortunately, a lot of old LCD monitors did not have short blanking timing included as part of their EDID (display driver).
The situation can often be corrected using a program like SwitchResX. Using SRX a custom timing can be built using the preset referred to as "CVT-RB" which stands for Coordinated Video Timing - Reduced Blanking. Use SRX to build a 1600 x 1200 timing with that option and all should be good.

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