A YouTube spokesman downplayed the blockage: “After tonight’s live stream ended, YouTube briefly showed an incorrect error message,” he said via e-mail. ” Neither the live stream nor any of the channel’s videos were affected.”

It’s not clear what he meant by none of the channel’s videos were affected as the video was unplayable.

The most likely culprit is YouTube’s pre-emptive content filters, which allow large media companies to upload content they claim to own and automatically block videos that an algorithm decides matches their own. That would make the glitch the second livestream copyright-policing snafu in the span of a few days: On Sunday, a similar algorithm at uStream interrupted the livestream of the Hugo science fiction awards. The award show included clips of copyrighted videos, though the algorithm didn’t know that the clips had been authorized.

In early August, an official NASA recording of the Mars landing was blocked hours after the successful landing, due to a rogue DMCA complaint by a news network.

MORE: YouTube Flags Democrats’ Convention Video on Copyright Grounds | Threat Level | Wired.com.