Guys I need your help I'm getting deperate here. My N800 wont boot up When I press the power button it shows the white screen with the nokia logo on it and then it reboot itself. Itried pluggin in the charger and nothin, the firs time it shows the battery logo but it soesnt say "charging", and then the screen black and reboots and starts a loop. Tried removing the battery for 5 minutes to 12 horurs and no luck, I even put the device on the fridge for about 15 minutes. Does anybody have any suggestion?

Can you boot into usb mode? I think its holding down the home key while powering on and letting go of home when the usb icon appears in the upper corner. If you can get there.. you can reflash the device to hopefully clear out what error you have.

Try disabling LifeGuard, can only be done by the linux flash, so you may want to download a livecd.

I know your pain, I have had the same problem twice in the last 2 weeks.
When you do get it working, lookup flashing a clean copied to a SD card with the modified bootloader.

Had that happen with mine the other day, perhaps the battery ran too far down, not sure. Would boot as you are saying yours did and just stop on the white screen or just go to black with the charging icon.

No luck with much of anything, figured it was toast (I'm just waiting for that). Put it on the charger overnight and with popping the battery in and out about a half dozen times or so the next morning and trying to boot, it finally came back up and now appears fine.

Ok, got it working again phew..... I had to reflash it, and install everything again. I tought that with the last os update this problem was solved but aparently not. Now every time I turn it off Im afraid this happen again, so I was thinking, would it be safe to leave it on all the time?, and is there anyway I can backup all my installed apps because it took me a few hours to get everything working again and I wouldnt like to go through this again.

By the way, thank you guys for all your support!!!!!!!

This has happened to me twice. It's very frustrating as the only way out for me was to reflash. The problem is somehow related to shutting off with less than a full charge so my solution is to never shut the device off, or if you have to shut it off (ie. for flying) make sure it is fully charge when you do. Also, keep current backups! and keep sensitive data on an external SD card.
I hope Nokia addresses this in the next OS update...

Mine never gets turned off now and is rarely off the charger anymore since the last lockup and massive masturbation required to get it back. Unless you consider the approximately dozen times knocking the battery out in the process of bringing franken800 back to life :-).

Seems to be much happier never turning it off and being very careful about not running the battery down too far.

I don't have any such troubles, thank goodness, but I wonder: Why would you have to shut it off for flying?
Isn't offline mode good enough?

Only turn mine off if an app spikes the procesor and I can't get the thing to respond. The last time I had problems booting the battery had been run down very low. This thing appears to be capable of drawing more power than the battery can supply at a times, so if that battery is near dead or dead, i can see this problem happening.

at least your touch screen still works