Hi, can anyone help me with my laptop problem? - very dark screen Acer Aspire 5735z?

Paiva..

So a few weeks ago my parent's laptop (Acer 5735z) suddenly stopped working, The screen flashes on briefly (1/4 second maybe) and then goes very very dark. The desktop is there but really dark. I've been trying to fix it.

I'm posting this question from that laptop now hooked up to an external monitor.

I've just this morning received the new inverter that I've been waiting for, because I thought that was the problem. however I've hooked it up and nothing changed :/ I'm not sure what else to do... any ideas?

It won't be a backlight problem will it? Because I think if the backlight had gone that I wouldn't see anything at all on the screen? One possible reason that it might have stopped working so suddenly is that the night before we had my 1 year old niece here and we were blowing bubbles for her and it may be that some water got on to the laptop and soaked through to the insides. I read somewhere that it could possibly be a problem with the motherboard.... however I really don't believe that that could be possible... to damage the motherboard so that the laptop screen goes dark but you can still use an external monitor fine...... Also the wires seem fine, there's no breakages or splits in them.... externally anyway.

Any ideas? I really don't know where to go from here :/