Basically, after months of trouble-free use, my N800 did not go past the Nokia logo screen with the white background and the progress meter at the bottom. While the progress meter was going forward, it restarted and again started the process, which basically had the same ending, which was another restart. This kept happening until I managed to turn
off the device completely, which also was not an easy task.

I thought their was something wrong with the battery, so I went out and purchased a new one. However, even with a new battery installed, the situation remained the same. So I returned the recently purchased battery and got a refund minus a 20% restocking fee (cheapskates, they are), and sent the device, it's contents, and packaging to the online retailer I purchased it from. They received it and agreed to exchange it for a new unit, so I haven't truly incurred any monetary losses.

However, I am still interested to know how that problem occurred in the first place. Would you have any ideas?

Sounds like a reboot loop - did you try enabling the R&D flags, disable the lifeguard reset or reflash? If you search for any of the aforementioned terms you'll probably find dozens of threads. It should definately be recoverable without sending away for repair/replacement.

The chances of a reboot loop have decreased significantly with the latest 3.2007 firmware however there still seem to be some corner cases that trigger it.

How do you do the following?:

1. Enable the R&D flags

2. Disable the lifeguard reset

3. Reflash

The problem occurred after I downloaded and installed the latest update from Nokia.

The clue was in my answer - search

Read this thread and follow the link in comment #6... you'll need a Linux PC in order to set the R&D flag or disable the lifeguard reset. If you don't have access to a Linux PC try downloading a Live CD distribution (DSL Linux works fine and is only a 50Mb download)

Instructions on using the Linux Flasher tool are here - put the N800 into "flasher mode" by connecting the USB cable then holding down the Home button while booting the N800. Once the N800 is in flasher mode, try the following in order...

1. "./flasher-3.0 --set-rd-flags=no-lifeguard-reset -R"

If the above doesn't work, try...

2. "./flasher-3.0 --enable-rd-mode -R"

Once your device is booting OK you can disable R&D and re-enable lifeguard reset as follows

3. "./flasher-3.0 --disable-rd-mode --clear-rd-flags=no-lifeguard-reset -R"

Chances are something is hanging during the boot sequence and lifeguard-reset is kicking in and rebooting the device - the lifeguard-reset is a mechanism to detect when the device has hung and automatically reboot the device... if the device hangs (or a startup process abnormally and temporarily consumes a lot of CPU) during boot sequence then the device will reboot itself forever. Did you install any apps recently or has it always looped since you flashed the last update? It's possible an RSS feed has corrupted itself... I think these have been a cause of reboot loops in the past.

Thanks, Milhouse.

Do not upgrade magic.sys while in red pill mode. Dude, just re flash with the nokia utility.