Two weeks after Time Warner Cable yanked its Fox, Viacom and Discovery iPad apps that allow its subscribers to receive real-time programming from them at home, the Fox and Discovery apps were again up and running on Friday, leaving Viacom as the only cable programmer still balking at TWC's iPad service. The return of such channels as Fox News Channel, National Geographic Channel, FX and Discovery Channel went unexplained. Contacted by reporters, both the cable company and Fox declined to comment. Discovery said that it does not discuss affiliate relationships. Viacom's channels, including Comedy Central, MTV, and VH1 remained missing. However, TWC added four other channels -- Sundance, Lifetime Real Women, Wedding Central, and Military History.