Liquid Spill Dispute--Anyone Have Advice/Similar Experience?

Question

I sent my 15" MacBook Pro into the Apple service center for repair because some of the keys had stopped working, it was making that infamous whining noise, as well as doing the equally infamous random shut off.
Apple is now claiming that the defects are the result of the insides being trashed by some kind of liquid spill, the warranty is void, and I owe them $1000 for a new LogicBoard. I can confidently say that I've never, ever spilled ANYTHING into that computer. Not beer, pop, juice, wine, or even water. Hair, dust, and crumbs I'll own up to. But an all-corroding spill the kind of which they're claiming has happened? Not a chance.
I've got no idea what to do. The representative I talked to today was NOT helpful--she just kept repeating the same thing over and over again. I'm not sure who I need to talk to or what I can do to get this thing repaired under Applecare.
Has anyone had a similar situation--or know of any possible vindication available to me?
macbook pro 15"   Mac OS X (10.4.8)  

Answer 1

Thanks everybody for all of your help and advice so far. I have a couple questions regarding some of your replies.
First and foremost, BeProf:
I've got a sinking feeling that you're right. You said you've been on both sides of the same situation. If you don't mind, can you elaborate on what happened when you were on my side of it?
When you guys (or girls) are talking about getting a second opinion or taking it to an Apple Certified Service Provider, are either of these options steps toward getting any use out of my warranty? Principle aside, I'm afraid my available fundage for this project is pretty much nil. Even if we're talking getting charged less than what Apple is asking, I'd probably opt to keep using my unreliable computer as is.
Boece: I know what you mean about an insurance claim--that's why I'm not seriously considering that route either.
No, no one used the word corrosion. "Liquid damage" was as specific as it got--no indication of what kind, how much, where at, what's broken, etc. All I know is that there's liquid damage and lots of it. I did go ahead and ask for pictures and more details, but I'm not crossing my fingers that the story is going to change. Not without some kind of ammo--is this what a second opinion will do for me?
No, I don't live near the ocean. The computer has spent extended periods of time in beachside neighborhoods (Venice, Colombia), but wasn't really getting opened or used. Never on a beach.
I don't know how much fight I have in me. I can make noise, or talk to people who will make noise for me, those are about the only tools I have at my disposal. I'm fighting hard with the urge to be self-righteous--I know that's not going to get me anywhere. But I'm sad and more than a bit steamed that this computer is looking more and more like a $2233 mistake and that I'm not even getting the redress that I paid for.