@jd4200: I think being a phone is intrinsic to the N900, so "you can use it fully (minus making phone calls)" is a contradiction in terms. Once the SIM card is gone, I can't get software updates, I can't use it as a GPS (the Ovi Maps app has to download maps), I can't use my automated rsync scripts that backup my N900 data onto the home server --it would be little more than a $20 Palm Pilot. It's true that if I happen to be in a place where there is Wifi, the N900 could hook up to that, but if I had to hang around a Wifi hotspot to use my smartphone, I could do that with my notebook computer, which even has the advantage of a DVD burner.

In any case, it doesn't work even after I take the SIM card out. Sorry if I didn't make it clear, but I had already returned my first N900 to the store. When I did that, of course I took out the microSD card and the SIM card before giving it back. I had to demonstrate to the store that it was still non-functional (otherwise they would not refund all my money), and it was not. While it is still possible that the bad SIM card or bad microSD card was the cause, we already know that once the problem is triggered it is not resolved by removing the SIM/microSD card (yes, I did try rebooting after removing).

@matthew maude: Thanks. Could you give me the link to Nokia's Maemo forum? I thought this *was* the Maemo forum.

@YoDude: That is scary if a symlink can nearly brick the device, but I agree that that might be something other people might not do, which would account for the "We've never seen your error on the N900 so there must be something wrong with you and not the N900."

@YoDude again: Thank you for trusting me to have eliminated the basic possibilities and not treating me like some idiot to be talked down to. Indeed, I have done my best to eliminate the possibility of corrupt eMMC on my N900:
- for a corrupted eMMC image, correctable by reflashing, I have reflashed (about 4 or 5 times).
- for hardware corruption of eMMC, I have actually returned my first N900 and bought a second N900
It's possible that that both N900's were from the same bad batch since I got them from the same store, but then that would speak volumes about Nokia's quality control and whether I should use Nokia products in the future.

@maxximuscool: I did reflash the eMMC and OS; sorry if I wasn't being clear when I said in the original post: "there is only one thing I've found which can make it usable again: I have to flash the firmware and the "eMMC" image ... (It's not enough just to flash the firmware.)" As for "reflashing" the "Memory card", I take it you mean the microSD card. I'm not sure what you mean by "reflashing", but I replaced the old 128MB card with a brand new 16GB card, and the error still occurs --I think that answers you.

I have returned my N900 for a refund.

I would say that, after having owned a N900 for six weeks without being able to prevent (or even identify the trigger for) the boot-up error, I cannot realistically rely on the N900 as a phone, much as I'd like to use it. One might say that I could have spent more effort debugging during these six weeks, but if I was too busy to do so, then realistically I won't be able to do so in the future, either. I need something that just works.

Who knows, maybe I'll still try buying it off Amazon.com for $450, hoping that it was just a bad batch that went to my local electronics store.

@dchky: Hey, I like carbonated diet beverages, too! You don't suppose THAT could be the problem, maybe? just kidding