Might be also that some 2.4GHz wireless phones interferes with the WiFi connection. I have one Vtech phone and every time it rings both my desktop and N800 gets disconnected from the AP. Needless to say that I'm no longer using that phone... Too bad you can no longer find those 900MHz phones that have no issues. Another alternative are those 5.8GHz phones but I'm afraid the RF signal is less capable to penetrate walls etc...

I suspect some of my neighbours have similar 2.4GHz phones since sometimes I get frequent disconnects without any good reason. If I try to reconnect most time I get the same error message than you. Then on other times the connection stays rock solid?

However, the N800 seem more sensitive to this than my desktop? It could be that the Transmit power level of the N800 is lower or the N800 antenna is less optimal.