Finally... I found someone else who has the same problem as me. I have had my N800 for 5 months and it has connected no problem to any and all wireless networks I needed it to.

Then one day last week, nothing. I would intermittently find some networks but on the next automatic refresh during polling, they would be all missing again.

So, I first tried a restore of an old backup (thinking it was a bad config some where). Nothing. I re-flashed the OS to factory settings (nothing). Took the battery out for several hours and restarted. Nothing.

I ended up sending my N800 back to the Nokia repair center. I will try to post an update when I know more.

F1fan.