I'm not 100% sure but it from what I've read it sounds like Sonic Youth's set got cut short because Calle 13 who were on before them played 25 minutes longer than they were supposed to, that's why the lights came on during Sugar Kane. Still Sonic Youth played a great set for about 1hour 20mins.
Here's my mp3 rip of the webcast.
http://www.megaupload.com/?d=8YZ4A2YQ
I don't think I will put the videos I got on youtube as they didn't turn out well but if anyone really wants to see them then I'll send them to you...