I got almost exactly the same problem:

Problem:
Display goes black (not blue as in no signal) and returns usually 2 seconds later
this repeats two to three times. Only on Westinghouse monitor not second monitor...
(but I cannot test dvi or hdmi connect to 2nd monitor without very expensive adapter)
1920x1280 native res. HDMI cable feels hot to touch on monitor end and screw for next port vga d-sub feels just as hot. I originally blamed the video card and installed venting in my chassis, but the problem remained even with lower temps reported in chassis. I have recently tried blowing over the vents in the back when it starts a "blackout cycle" and have seen fewer "black outs" repeats.
So I'm contemplating attaching 40MM fans to help vent from the upper slots in rear.
Any better ideas, criticism, or solutions are welcome short of purchasing a new monitor.

Setup:
Westinghouse L2410NM (24" monitor, HDMI, component, composite, vga, and audio)
via DVI-HDMI cable from ATI Radeon X800 Mac Edition (Power Mac G5)
alt display 17" Apple studio Display LCD
via ADC (Apple proprietary connector power+signal)