Inverter probably. Sometimes the inverter can shut the monitor off if one of the back lights is on the fritz, though, so that could be the issue as well.
When you turn your monitor on, do you get a picture for a few seconds and then it shuts off, or does it shut off immediately?
i don't get a picture at all. nothing is ever displayed...
If it's not immediate, are you sure you're checking the screen with the flashlight while it's on?
While I'm sure you already checked those, it wouldn't hurt to check every connection again to be sure they're tight.