Dish Network, which has nearly 500,000 customer homes in the Los Angeles area, is locked in contract talks with Viacom Inc. trying to reach a new carriage agreement to carry on screening 18 Viacom channels including MTV, Comedy Central and Nickelodeon. Viacom’s stock has plunged in the last year and the company could lose as much as $700 million if Dish were to drop the channels permanently, reports the Los Angeles Times.