Mac OS X DNS lookups take forever from Safari and other applications that use mDNSResponder. The same lookups work fine if I use nslookup from the command line, and they also work fine from my iPhone and iPad on the same wireless network.
And that's only on the network at work; when I'm at home, or tethered to my iPhone, all DNS lookups work fine. When I'm on the network at work, either via Wi-Fi or Ethernet, I have these problems. I've tried using the following commands:
launchctl unload /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist launchctl load /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist
That used to provide some temporary relief (minutes) under Snow Leopard, but now, under Lion, it usually doesn't provide anything at all.
Neither my Ethernet nor Wi-Fi settings specify DNS servers; they're auto-filled from the router. But I have tried specifying my own, like Google DNS or OpenDNS, and that doesn't fix the problem.
The network setup is a router plugged into the cable modem, with all Ethernet ports in the office coming off of it. An Airport Extreme wifi router is also plugged into the main router (in bridge mode), and the WiFi clients connect to that.
I've searched all over and found other things that look applicable at first (e.g. DNS lookup problems Mac OS X - but nslookup works!), making me think that these mDNSResponder issues aren't too uncommon, but none of them exactly match and their solutions haven't worked for me yet.
Also: it's not every DNS lookup, just most. Google searches come up instantly, but Google Maps takes forever to load (when I look at the activity window, it's usually scripts and whatnot coming from some Google CDN server). Even sites that we use every day, and you'd think would be cached someplace (like php.net) take forever to load, or time out.
Also: everything loads fine from a browser within a Windows XP virtual machine, which to me points even more accusingly at mDNSResponder as the culprit - but everything works fine when I'm any other network.