Video output problems?

I am in desperate need of help before I start tearing my hair out. I have a Macbook OS X 10.6.8. For several months I have had connected a Samsung SyncMaster P2370 monitor attached via VGA-mini DisplayPort. I've never had any problems whatsoever until today. I pressed Shift-Command-Eject (I meant to press Option-Command-Eject) and it started playing up.

First the external monitor went to sleep. My macbook still worked as usual but when I moved the mouse over to the extended desktop on the external monitor it remained black (though itunes, which was open on the external monitor, continued to play). During my attempts to revive video on the monitor, which included putting the whole laptop to sleep and then waking it up again, restarting the computer, unplugging the monitor and replugging it, the display would randomly wake up, work fine for anywhere from 10 seconds to 3 minutes before going back to sleep.

Then however, after one episode of restarting the computer, the external monitor no longer registered at all as being connected. Now I can't even get my macbook to recognise that there is a monitor attached at all. I've been trawling through the forums and using google to try to find an answer. The closest I came is someone who mentioned that control-shift-eject may turn off video output. Nothing about shift-command-eject. And even if this is what has happened, I can't work out how to turn it on again. The fact that it started exactly when I pushed these keys makes it seem likely that it is not a monitor or connection problem, but I'm still stumped.

Help!!

Let's reset the System Management Controller and see if that works. See this LINK. Also, reset the Samsung back to factory default from its built in menu. Post back results.

Okay, so when I first got home after a few hours out I woke up my laptop and the monitor came on too, with picture. That lasted about 30 secs, then went black but still registered on my macbook. But then the screen flashed blue and the external monitor was no longer there. Then continued to flash blue with nothing happening.

So then I tried resetting the System Management Controller. Nothing seems to have happened. Same story, when I turned it on it didn't register the external monitor. When I clicked 'detect displays' it read it, but the external screen stayed black. Not even a minute later the blue flashed, ext monitor no longer reading and continued to flash blue.

As far as using the menu on the Samsung monitor, that was one of the things I thought of to try back near the beginning, but with a consistently black screen, nothing happens when I push menu. The only thing that has happened more recently is that when I pushed menu a couple of times, the top left corner came up and said 'test good', but still nothing happening.

It's been frustrating because it's always been so good. I've never even had to push detect displays before today because it automatically registered the monitor connected whether it was connecting before the laptop was turned on or after. How could pushing those three buttons have screwed it up so much when it's been so good? Seems crazy.

Resetting the SMC should have worked. I'm inclined to think it's a hardware problem with the monitor since you mentioned about trying to reset the Samsung from its menu and it didn't work.

The next thing to try before assuming it's the Samsung, it to test it on another machine. You can try attaching it to another Mac or even a PC to see if it responds. If it doesn't and the monitor is still under warranty, contact Samsung for a RMA.

It's definitely not the monitor. Admittedly I'm too wary of damage to transport the monitor to attach it to my mother's beast of a computer, but I did try plugging another monitor that I have (and that I know works just fine) into my laptop and it would only say 'no signal'.

In the meantime my aunt suggested I try using the OS X install DVD to run checks on the disk functions but everything there checked out ok.

Man, at this rate I don't think I'll ever use keyboard shortcuts again after this.

OK. That leaves us with the cable or adapter that may be defective. Try replacing both. Also make sure the cable and adapter are securely fastened to their connectors. Let us know.