4 month old 13" will not boot

Question

Hello all,
My brother bought a 13" MBP back in September. He hasn't had any problems with it (except for Flash working intermittently) until now, but this is something I've never seen before.
He brought it home from university halfway through December and told me he couldn't get Flash working. I should probably point out he doesn't really know how to sort these problems out, so what followed was a bit strange. He tried installing Flash again, then uninstalled it, tried again, then for some reason used Appzapper to delete the installer... Appzapper unexpectedly quit during this, then apparently the MBP became very, very slow to respond to anything.
The first thing I did was attempt to verify the permissions, but Disk Utility hung almost immediately. Then I booted the MBP off of a Snow Leopard disc (a shop bought one, not the one that came with the MBP) to run the Apple Hardware Test; this came back fine, no problems reported.
I then tried booting off the SL disc to run Disk Utility, and the strangest thing happened: I got the kernel panic screen (the one informing you to force shutdown your computer in several languages) at the booting screen, about 10 seconds after the chime while the spinning loading icon was still spinning. This was strange, I've been using Macs for around 16 years and I've never seen that.
I tried booting it off the internal hard drive again; this still worked, but it was still very unresponsive. I reset the P and NVRAM, this didn't help. I tried safe booting it (holding shift while booting); a progress bar came up, got about 1/10th of the way through, disappeared and then it kernel panicked again.
Then I used Target Disk Mode on the laptop to use Disk Utility on my Mac Pro to verify the disk, this came back with errors (invalid file count and something else), but Disk Utility claimed to have fixed it. For some reason I was unable to verify the permissions, though. I backed up his files while I had it Target Disked, then booted my Pro off the Snow Leopard disc. From here I still couldn't verify the permissions, so I went ahead and installed SL on the MBP's hard drive through firewire (I hope you're still following!). My Pro then rebooted off of the MBP's hard drive, and everything was fine; his system was untouched and perfectly responsive.
So with the fresh SL installation I rebooted his MBP, and guess what: It no longer wanted to boot; it just kernel panics straight away. I used the same method to zero all the data on the MBP's hard drive and reinstalled SL from scratch, and it still won't boot.
After all this I can only conclude that this is a hardware issue. I was under the impression that the chime indicated that the processor had been found, so I presume it's not a logic board fault. The optical drive worked (when I first target disked it to my Pro the SL disc was still in the drive and showed up on the Pro), the battery is apparently fine, no doubt the hard drive still works...
Could it be the memory? More to the point, would his warranty be void if we were to open it up to reseat the RAM? I presume you just take the bottom plate off? If that's all it is then we could save a trip to the Kingston Apple store...
Cheers!

Answer 1

A few things: first, RAM is customer installable, so no, you don't void the warranty by reseating the memory, as long as that's all you do.
I normally would have said, oh yeah, sounds like the hard drive, except it seems to boot your computer in target disk mode, which is odd. I'd say given that TDM works to boot another machine, the HDD is probably not the cause, nor the HDD flex cable (which connects HDD to logic board).
It could always be a logic board issue, though you're right, the chime does indicate a basic level of functionality. This means the Power On Self Test (POST) has passed, and means the processor is able to detect and address the memory. The logic board is a lot more complex than what the POST checks quickly, however, so the logic board isn't ruled out by the fact that the computer chimes.
Memory is always a possibility, especially if the first symptom was flash not working. The graphics chipset could also be a possible cause.
You've got a few options for troubleshooting. I'll list what I'd do in order, and you can try whatever you feel up to.
First, I'd boot the machine from its internal drive in verbose mode. Do this by powering it on, then holding command + V down till you see white text on a black screen. This will boot the machine normally, but it will show you what it's doing. The advantage of this is that if/when it panics, you can see the panic log. If it's booting far enough, we might be able to see what it's getting stuck on. Anything graphics related, like SystemUIServer or anything referencing nvidia could indicate RAM or graphics. This would likely mean the computer is panicking when hardware video acceleration is kicking in, about when you'd see the blue screen during boot. If it panics pretty early in the boot sequence, you might not see anything helpful in the panic log.
If this is inconclusive, the next thing I'd do is test booting the machine with individual sticks of RAM installed. Make sure you're grounded, or that you're able to reasonably ensure you won't be shocking the computer or any of its PCBs. Don't work on carpet, don't wear polyester or fleece or have any nonconductors like styrofoam or plastics around, and touch something metal to discharge any static electric charge your body may have before touching the RAM.
The next thing I'd try would be to run the Apple Hardware Test. You can do this by powering on the machine, then holding down D on the keyboard for about 30 seconds. This is a test that runs in EFI (firmware) and has no video acceleration, so if the computer chimes and has video, you should be able to run it. You'll want to check the box to run extended testing, then walk away for an hour or two. If it comes back with an error code, you can take that to AppleCare or your nearest Apple Store and they'll know what hardware component to replace.
If all else fails, you'll probably have to take it in. It sounds like you've ruled out software though, which means you've got a hardware problem either way, so whether you want to troubleshoot it or let Apple do so is up to you.