DNS resolution appears to be inconsistent across OS X for no reason I can fathom.
$ ping example
PING example.co.uk (80.94.32.224): 56 data bytes
64 bytes from 80.94.32.224: icmp_seq=0 ttl=56 time=62.077 ms
Yet:
$ nslookup example
Server: 10.20.20.1
Address: 10.20.20.1#53
** server can't find example: NXDOMAIN
http://example/ resolves in Firefox, yet:
$ dig example
fails. I am pointing at my router's default DNS (10.20.20.1, as above). Pointing to other DNS servers does not appear to alter the above behaviour.