Shohreh, a 37-year-old Iranian nurse, sat down with her husband and parents one night in September to watch a documentary about Iran's supreme leader, Ayatollah Ali Khamenei, scheduled to be shown on the British Broadcasting Corp.'s BBC Persian channel. But when the Tehran family settled on the couch with a bowl of pistachios and switched on the television, all they saw was scrambled imagery. The satellite signal was being jammed.