Macbook chronic hangs on startup

I'm on my second Intel Macbook (SR 2.2Ghz), after using it for just over a month. Three times now the computer has spontaneously failed, hanging indefinitely on startup.

First time I switched to another macbook, assuming a hardware defect. Second time it happened was the very day after moving to the new machine. I let Apple talk me into keeping the machine and doing an erase & install, assuming that it was a software problem (Rosetta?) after all. So I hardly installed any new programs, just print drivers, Office 2004, and a couple other pre-Intel apps that behaved fine. Hadn't installed anything new for a week when suddenly--SAME PROBLEM. This time it gets past the apple and spinning gear and reaches the blue screen, only to reprise the spinning gear, ad infinitum.

I'm thinking there's some chronic hardware malfunction with the macbooks or else I have the worst luck in the world. Repairing permissions fails. Fsck doesn't do the trick. I'm out of answers and so is Applecare. Even though I'm past return/exchange period I'm thinking all I can do is go back to the store and demand another exchange.

Anyone else out there with this same, chronic issue??? HELP?!

You know that's the weird thing: I installed 2 x 2GB of Transcend RAM into the first macbook and it worked fine for about a week, after that the problem presented. So, following the switch to the new machine I held off on installing them, but the same problem occurred right away. So after the erase & install and using the machine for a week I reinstalled the same chips and then a week later...same result! So I was thinking it was the RAM, as that explains the error the 1st and 3rd times, but that doesn't explain the 2nd time! On both occasions I switched the original RAM back into the machine and it didn't change the behavior, so that it means it can't be a RAM problem, right?! (or can 'faulty RAM' corrupt the directory or something?)

No Third-Party apps after the first two failures. I've pretty much just been using Apple and Microsoft apps, along with the drivers and apps that came with my Canon printer. Other than those I'm not using any of the programs I installed before the 1st and 2nd failures.

Could it be a RAM issue this time? The brand of the original RAM is Hynix. Should I try to get those chips and ditch the Transcend brand?

[Also, the Apple retail people made it sound like your warranty gets voided if you install non-apple RAM, but I never saw that in the documentation; I'm under the impression it's the same "at your own risk" type of warning they always give, not an all out voided warranty. Anyone know for sure on this?]

Has anyone had problems returning/exchanging in situations like this after the 14-day window?

I figure it's a retroactive problem because they know how it failed on me the day after I got it, but I don't know if they'll give me problems with an exchange...since they likely only have the newer penryn macbooks in stock (if they allow it they BETTER throw in the freakin' remote).

Went to the store today and they gave me one of the brand new blackbooks and eventually threw in the remote (only after I whined enough).

But seriously, it is just plain rotten to remove items like the remote (and the Mini DVI adapter, as they did before) after offering them standard. It should be criminal to tout the 'features' of a product as they do, only to nickel-and-dime the buyer after the fact for wanting to use them. Shame on you, Apple.