" the problem is non-existent on some resolutions and back again with others)"
To me this nails it as the display is mis-rendering the VGA signal. Sadly to fix this you need to try other than VGA connections or change the display. Also, if you can control the refresh rate, drop it to 60Hz.
"I've tried the monitor with a Windows laptop, as a 2nd screen. and there was purple pixels on the desktop wallpaper."
You've proven to me this monitor has issues not in the actual LCD but in the circuitry that renders VGA to the LCD.
my monitor - HP LP2475w. running at 1900x1200 res
my computer - Dual 1.8Ghz Mac G5
I know this is a PC hardware forum. But bare with me please.
my problem - i have green (sometimes pink, once red) flickering pixels on some parts of my screen. They are not always in the same positions, in fact they move in accordance to the image currently on the screen.
here are a couple of photos I took to better illustrated the problem:
http://www.willarbuckle.com/knuj/pixelexample.png (pink vertical line, 1 pixel wide)
http://www.willarbuckle.com/knuj/greenpixels.jpg (when moving the window, the green pixels will move with it)
I've tried the monitor with a Windows laptop, as a 2nd screen. and there was purple pixels on the desktop wallpaper.
I had a cheaper LCD monitor about a week ago (returned it because it wasn't very good quality) but it worked fine with my setup. same resolution etc.
So I suppose all these experiments point at the monitor being faulty.
But when I change the screen resolution. the problem is non-existent on some resolutions and back again with others)
I've just swapped the standard DVI-D cable with a heavy duty DVI-I cable as both the computer and the monitor female ports accept DVI-I, so I thought it was best to give it a shot. But this gave horrendous results: see here: http://willarbuckle.com/knuj/redngreen.jpg plus the whole screen flashed on and off repeatedly.
I'll send the monitor back to HP but was wondering if anyone had any ideas to what causes this?
I suppose I'm just a bit reluctant because I've already had to send back another monitor and it's a hassle. Plus I've read on other forum posts where people have had several displays replaced... but had the same problem on each new display. There's actually a discussion over on the apple forums that's lasted about 2.5 years with no one solving the problem.
Any ideas? Thanks,