Macbook Pro LCD Screen Works Sometimes / On/Off

For several months my (late 2007, 15 in) macbook pro screen was not working at all. I took it to apple at one point and they said I would need to replace my screen which would cost at least $400 or $600 I can't remember how much. I just knew it was too much.

Then recently I found out that my model had the NVIDIA GeForce 8600M GT graphics processor and Apple found out those had a problem in a number of those computers so they are supporting it by replacing the mother board.

So... I got my new mother board recently but the screen was STILL not coming on at all after the repair. One conclusion was obvious I needed a new screen or just use the computer as a desktop with an external monitor which is what I've been doing.

So now, here's the rub:

My SCREEN MAGICALLY HAS COME BACK ON just last night and this morning... it was working and then Poof it went off again.... now again it's magically come back on.

When working there isn't any streaks or anything that appears damaged on the screen at all. My guess is that there is some cable or some connector point that is loose and somehow like a short makes it go on and off.

Now, part of what has been going on since yesterday is that I just replaced my hard drive so I've had the cover of the computer off... somehow I did something to they keyboard so I'm having to use an USB keyboard right now (might have to replace that too). So... somehow my taking off the cover and putting it back on a few times must have touched something that is making it work again.

What could it be? Any ideas? I'd be grateful for any advice that would keep me from having to try buying a new screen as I understand I have to replace the whole piece.

Thanks,
phil