From what I know, your TCP/IP stack is hosed. Theoretically, reinstalling/reinitializing it by issuing

netsh int ip reset resetlog.txt
[download]

should work magic. tachyon tackled the same problem and found a solution, so maybe that will help you. Should that not work, you'll have to reinstall your OS.

Update: Changed order of last sentences and added a link to tachyons solution to the problem instead of just the main thread.