This week, some TiVo owners reported receiving a message telling them that they couldn't store their recordings of Family Guy and The Simpsons because the copyright holder had set a flag preventing this.
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TiVo says that the two programs that got this flag received it as the result of a transmission error -- noise that was "misinterpreted as a copy protection signal."
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Charitably, an operating system vendor's rep suggested that TiVo might not be lying: rather, he said that perhaps they've just done an "incredibly bad" implementation of Macrovision.