Advertisements or other types of targeted information are delivered to set-top boxes or other user interface devices of a signal distribution system. In one aspect of the invention, at least one multicast update comprising updated targeted information is sent to the user interface devices during a multicast update period. If a given one of the user interface devices is unable to obtain a complete set of the updated targeted information from the multicast update before timeout of the multicast update period, a unicast update comprising at least a portion of the updated targeted information is sent to the given user interface device during a unicast update period. The unicast update may be sent responsive to a request from the given user interface device for a designated portion of the updated targeted information.