Ok, it's an AMW A911B 19" Monitor - A few months ago I had a few blown capacitors that I replaced in the power supply unit in the monitor.
System is Asus m2n32-sli deluxe, evga geforce 7900gs, 1280x1024 32-bit color. XP, DirectX 9.0c, up-to-date nvidia drivers. This was not a sudden change, it's been setting in slowly for a while.