UPDATE: Good news, tennis fans. No thanks to NBC, you can watch the semifinal live here, on ustream (ESPN Spain). And here's another, better one, in English.
UPDATE 2: It's noon ET, and NBC has finally started broadcasting. As expected, however, the network idiots have decided to show the match on a 2-hour tape delay (online, too!), so it's not worth watching. Click the link above to see it live.