ws 10.0.1 on win764
Have a wireless adapter in a disconnected state (hardware off, OS state "not connected") , it has no static dns configured, the DhcpNameServer key of the corresponding interface (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Tcpip\Parameters\Interfaces) keeps the dhcp configured dns server from the last time it was connected. And the nat dns resolver send its queries to this server first, slowing them down by several seconds, until they time out.
Now that I've figured out what was going on, it's easy enough to work around, but this is very stupid default behavior. It should exclude name servers from disconnected interfaces, and the name server from the default route interface should be first.