According to this CBS report, the United States dropped a bomb designed to take out Iraqi television by emitting an electromagnetic pulse to fry the broadcast equipment.
According to CBS,
The highly classified bomb creates a brief pulse of microwaves powerful enough to fry computers, blind radar, silence radios, trigger crippling power outages and disable the electronic ignitions in vehicles and aircraft.
Iraqi TV did go off the air for several hours. It returned to broadcasting later with a weaker signal.
MSNBC is reporting, however, that Iraqi TV appears to be off the air again.