3DS won't fully boot up, but I can force update?

I have my release model 3DS that I'd like to repair and give to my girlfriend, but there's something wrong with it.

When I boot it up, I hear a small pop like the speakers engaging, but the screen stays black. I can tell that the screen is lit, it just stays black.

What's odd is, I can force the unit to search for an update, and that whole process works perfectly. It will connect to the internet and I can watch it progress and the sound works exactly as it should. I'm perplexed here.

Proof the 3DS will update: http://i.imgur.com/oU970A2.jpg

What could I try? Before I just gave up and bought an XL, I tried reseating the wifi card, but that didn't help anything. I remember exactly when it broke if that helps, I put it in sleep mode one night and it worked fine. The next morning? Wouldn't work anymore.

Not really worth it for me to send it to Nintendo to repair (for $100!), I just thought she might like to have a 3DS so we can play games together.