My N800, running Diablo, has suddenly developed a problem in that DNS isn't working. My laptop uses DHCP, has exactly the same settings as the N800 and the DNS works.

I've been using vpnc a lot recently. It still works, but now gives me an error message that it can't find /var/run/vpnc/resolv.conf-backup.

Any ideas how I can fix this and what might have caused it in the first place?

I think it is related to the problem described here but I don't understand the solution.