A guide data server stores program guide content in a memory and transmits the stored content to a multicast server. The multicast server transmits the received content to set top boxes according to three independent time periods. The three time periods include an update blocking time period, a multicast blocking time period, and a normal time period. During the update blocking time period, the multicast server transmits old program guide content to the set top boxes. During the multicast blocking time period, the multicast server (1) performs a one-time request for the new program guide content from the guide data server, and (2) receives new program guide content from the guide data server. During the normal time period, the multicast server receives new program guide content transmitted from the guide data server and transmits the new program guide content to the set top boxes.