Gateway LCD powers on but has no picture

I have a Gateway FPD1730 LCD monitor. When I plug it into my Gateway 500x desktop the power light turns green and then says "Power Saving Mode" and then it goes black. It will occasionally flash on and have a picture and then go off. When I unplug the VGA cord the monitor says "No signal found". I know the screen is working because is shows the picture and it's fine.

I initially though it was the video card so I switched it out. I was running an NVIDIA 128mb AGP video card and I replaced it with an extra I had. I am now running an ATI 128mb AGP card. I then came to realise that it wasn't the video card at all. I connected my Dell CRT test monitor with the old video card and it works without a problem.

What can I do to fix the monitor? I would really prefer to not have to buy a new one. It seems like a semi-simple fix because I can see the picture on occasion.

Thanks in advance!