Macbook air mid-2012 w/ Mountain Lion.
Whenever I wakeup from a long sleep and also on some random moments when it's on, i get DNS resolution failures for every server, with nslookup saying
;; connection timed out; no servers could be reached; however, direct connections to IP addresses work correctly, since (among others) Skype works perfectly.
This resolves by itself after more or less 5 minutes, when DNS resolution gets back to work correctly, both with nslookup and in other applications (browser etc.).
I have Google's DNS servers (188.8.131.52 and 184.108.40.206) configured both on my network preferences and on my wireless router's settings.
Possibly related but still unsolved: DNS gone after wakeup