[Petya V4sechkin]

fugi1, суть в том, что наличие протокола IPv6 в некоторых случаях приводит к такому багу. На микрософте я не нашел объяснения, только статью KB555059.

Зато по этой ссылке похоже на правду:

Some users disable IPv6 functionality in their operating system to "increase their connection speed" behind faulty routers or ISP connections. This should not be an issue for most users but does occur quite often. The real issue here is that when a host becomes IPv6 enabled it will start doing queries for 'AAAA' DNS records. As some routers (actually a NAT box) or the upstream DNS have faulty DNS implementations, instead of answering the questing for an 'AAAA' DNS record, they simply ignore the question, not answering at all. This causes the computer to wait for the timeout, after which it will try to ask the question again, but now for an 'A' DNS Record, which will result in a working answer from the DNS server.