I have the same issue, "no signal detected" when using dvi or hdmi. The macbook (2,2 SR) detects g2400w properly only when it's connected to the monitor via dvi and the monitor is set to hdmi in, or vice versa. When I change to dvi in, macbook instantly drops the monitor, and "no signal detected" is displayed on the external monitor. No matter what resolution i choose.
I'm pretty sure it's an issue somehow related to EDID-signal sent by the monitor. And what is strange, there's one way I manage to get anything displayed on the monitor: first i shut down the computer, then plug it to the monitor with dvi, set the monitor to hdmi in, start the mac and close instantly the lid, and then change the monitor settings to dvi in. This way i can see the white startup screen with the gray apple displayed in the middle, which, however, disappears just before the logon screen and "no signal detected", again.
The strangest thing about this is that i somehow managed to get it work ONCE, when testing several times different versions of the routine i described above. I could get it working just as it should, log on and tested hd trailers and such but since the next time i turned the monitor off, it has been as dead as before. Any suggestions???