NewsTalk Television, the fledgling cable network owned by Gannett Co., is shutting down, according to an executive with knowledge of the situation. A number of NewsTalk's 3 million full-time subscribers are expected to get MSNBC as a replacement. The network, which launched on Oct. 1, 1994, was sold to Gannett earlier this year when it bought Metromedia. At one point CBS had spoken to Gannett about taking over the network, but those talks were not fruitful. NewsTalk did not return calls at presstime..