Sorry for digging up old threads, but i just bought a Mac Mini and i'm having the same issue. The monitor
goes black for some seconds. I also tried using a lower color depth but that didn't seem to help.
I have a Mac Mini 1.42GHz with 32MB Gfxmem (afaik).
I'm using DVI -> HDMI-adapter and i'm using 1920x1200 and also use a KVM (but only for mouse/keyboard) HDMI-cable is connected directly from the DVI->HDMI-adapter of the Mac to the monitor.
It worked fine on VGA here too, but the picture quality was pretty bad, so it's not really usable.
Is there any solution to this problem?