Crap.. I got the same problem. It does not see any network even my own.. And when I find it I get connection error. After having it charged a bit suddenly I notice it is online.. But if I take my n800 with me at work/make it offline and then online again it suddenly got the same problem.
I just yesterday decided to take a firmware reinstall again but now I am not able to do firmware upgrade either since the upgrade software don`t detect my n800 anymore. I have the usb symbol when I boot with the homekey pressed and I have done this one time before without any trouble so not sure what this could be.
I have tried to make it totally "dead" by taking out the battery and leave it out for half a minute before putting it back and try the same method to connect with upgrade.
Anyone have the same problem?