I bought an N800 a few weeks ago and it worked fine for a while. I used it to get on the internet and do various things that seemed normal. One day it just keeps rebooting over and over so I eventually have to pull the battery out to stop it. After this it would only turn on for about three to four seconds before shutting off again. I looked around on the internet to see what the problem was and it seemed some sort of update to something or the other normally caused that to happen, I'm not exactly sure, but I sent it back for a new one. The new one came yesterday and it worked great. All I did was put the SD card into it and allocate some virtual memory. I haven't gotten on the internet at all; it hasn't even had the opportunity to, and now it is having the exact same problem.
Does anyone know what the matter is, and/or how to fix it?
Thanks.

There is no one cause for what is happening to you.

Have you reflashed to the latest and greatest firmware?

That is how you can get back to zero, anyway.

Also, you might try removing the sd card to see if it has anything to do with your problem.

Yes, it's a bug. Reflash it with the latest Skype-enabled firmware and you should be OK.