Plugged in, but battery % remaining keeps decreasing

Hey there!
I was just using my 9880 like normal, when I suddenly smelled something like an electrical fire or burning plastic. I couldn't tell exactly where it was coming from (wasn't even sure it was my laptop). I had JUST started playing a video game with the fan on full throttle (fn+f2). I quickly shut it off and left it that way for about two hours.
When I turned it back on, I happened to notice that my battery indicator said "charging", which is weird because I've always had this machine plugged in. I've never run it on batteries. It was at 98%. The weird thing is, the % remaining is going DOWN. It's now on 75% after about 20 minutes.
I'm not sure what to do here. I'm a little afriad of what'll happen when it hits zero. Will it shut off, or is this just an indication that my battery got fried, and it'll still work because it's plugged in?
Has this happened to anyone else before?

Thanks for any help.

This is what I thought at first as well, and no doubt it could be true. What confused me was that the power indicator in the Windows tray showed that the computer was running off AC power, and that it was charging the battery (the plug with lighting bolt over it). This could, of course, just be misleading, but it threw me for a loop last night.
Do you think there's a possibility the battery or the connection to the battery got friend? Would that cause these symptoms?

In any case, thanks for your help. I'll probably e-mail Sager today or tommorow and see what they think.

Well, thankfully in my case there was no puff of smoke, and my laptop will still turn on. I'm just wondering what happens when it hits 0%... will it shut off or can I still run off AC? That'll be the real test.
Regardless, I'll call 'em up and see what they think. I also doubt it's the brick, but you never know.

small but sad update - it got to 0% and shut off. Sager hasn't gotten back to me yet. I would expect them to today sometime.
This would imply to me that it might be the brick, but could also be the mobo like doggie described... that would suck. The light on the brick still shines, but I'm keeping my fingers crossed.

This is exactly what I did. Unfortunately, it won't even get to them until Friday, so I can imagine that I wont have it back until the following Friday.
DOH!

I broke down and bought a desktop. I've had 3 fatal problems with this laptop so far, two of which have required me to send it back to Sager. This is in less than 6 months of ownership.
I love this laptop, but it just seems to me that gaming laptops aren't quite ready for prime-time. They heat up far too quickly, and the difficulty in swapping parts makes it even worse. It seems that Nvidia has already figured this out, since they don't officially support the laptop versions of their cards (another big problem I've run into).
Since this laptop isn't really portable anyway (12 lbs is a BIG load to be carrying around in a backpack), my primary reason for buying a laptop was for the small footprint (for a small apartment) and ease of moving (I'll probably move several times in the next several years). But those two benefits don't seem to be worth the cost of constant repair, let alone the bummer of unexpectedly being without it for weeks at a time.
So it was great while it lasted, but I'm sadly relegated back to the realm of kicking a huge box under my desk, at least for the time being.

Yeah, it's actually in the shop now, but unlike malignite13, I didn't wait patiently for it.
Go my Dell XPS last night. Let me tell you, in a slightly OT way, that the Dell XPS is to other desktops as my Sager is to other notebooks. The thing is HUGE. I bet it easily weighs 50lbs, and I had to haul it up 4 flights of stairs. WOW.
Anyway, if anyone else is thinking of getting a desktop, I would recommend something slightly... smaller.