I think I've been having something similar for the past 2 weeks or so. Maybe once every 2 days my N800 will have the problem wherein it will connect to a network, but once it does, DNS doesn't seem to work. Once that happens, nothing other than a reboot seems to fix it. I haven't had a chance to check that resolv.conf.wlan0 file while it was in the midst of the problem, but I wouldn't be surprised to see it had the same issue.

Alas, I don't know the fix either. I can say that reflashing, however, is *not* the fix (at least in my case), as I reflashed twice and still had the problem.