I've got a Ubuntu 10.04 laptop, and recently it's had some odd networking problems. It's on the home wireless router, supplied by the phone company, and has no problem talking to anything on the wireless LAN, whether by IP number or /etc/hosts name. It's set to use the wireless connection with DHCP, and there really isn't much I can screw up after that for network entries.
Right now, I can reach outside the LAN by IP number, but that doesn't do well for web surfing. When I do a nslookup, I'm getting non-authoritative answers, so I suspect I'm hitting a cache somewhere (probably the router). Any attempt to get outside the LAN with a domain name fails quietly, like a "can't find" using Firefox.
The only things that might have changed since it did work right are 10.04 updates (and there's been quite a few of them) and a couple of lines added to /etc/hosts, to address fixed IPs on the LAN (in the 192.168.0.* range). The lines are in the same format as others, and it's nothing I haven't done before with no ill effects.
Any ideas on what to try next?