MacBook Pro 15" randomly shuts off

That kind of sounds like an issue with the way you're handling the system. I know there was a long term issue with some iBook G4s, where solder joints started cracking due the repeated stress of people picking the system up and holding it with only one hand. As laptops get increasingly thin, this is a bigger and bigger issue.

Make sure you always pick the system up by grabbing it on both sides. If you can't use both hands, set it back down until you can. Also, for the longevity of your HDD, it's not a good idea to move the system while it's turned on. Portable on a laptop means it's easy to move when you've turned it off (or at least put it into sleep mode).

All in all though, I'd say it sounds like there's an issue with the logic board. So until you get it fixed, I'd say keep the thing as stationary as possible. Put it on a table or something, and get yourself in habit of picking it up with two hands if you aren't already.

You can also try running Apple Hardware Test. It may tell you more specifically what's wrong. Just pop in the OS install DVD and boot holding down "D". It won't fix anything, but might speed along repairs if you can tell the tech what was reported as wrong.

Mine started doing this a while back. I had always relied on the alert that told me I was on reserve power and then I watched the percentage numbers click down, knowing I was going to have to plug in to AC. But then I noticed that sometimes, even when I had 15% or so battery left, the computer would sometimes shut off without warning. This was unfortunate on some occasions when I was in the middle of working on a document. What I found out was that my battery was pretty much worn out (you only get about 300 cycles out of a battery). You can check to see how many cycles your battery has endured so far by going to the Apple menu, click more info, then click Power. Somewhere it will list your battery condition and how many cycles so far. If it's more than 300, you will continue to get those unexpected shutdowns until you replace the battery. Hope this helps.

Hey guys, mine is doing this too and only when it is on battery power, so I thought it must be the battery... but it has only hit 208 as opposed to 300... Could it be overheating? I had the fans replaced last year, but it runs quite hot. Thanks for your discussions!