MediaPost lists 21 cable networks whose coverage area ratings have been overstated by Nielsen over the past six months. Included are some fairly established, mature channels, like E! Entertainment, National Geographic, Oxygen and Versus. Last week, Nielsen began informing clients that it had understated household coverage estimates for about 20 networks since at least October 2007 because of a problem in measuring data from satellite TV distributors. This resulted in an overstatement of the ratings for those networks' coverage areas during the period. The list includes smaller to medium size channels such as: Biography Channel, Discovery Health, DIY, G4, Golf Channel, Great American Country, History International, Investigation Discovery, Military, MUN2, NFL Network, Nicktoons, Outdoor Channel, Science Channel, Style, VH1 Classic, and WGN.