Corning (GLW) - Get Report was down 10.3% in preopen Instinet trading after warning late Wednesday that the market for telecommunications equipment might soften in the first quarter. The maker of fiber-optic equipment posted fourth-quarter earnings of 34 cents per share, beating the Street's estimate of 28 cents and the year-ago 18 cents. It widened its guidance to a range of 28 to 31 cents per share for the first quarter from a previous prediction of 29 cents to 30 cents. Merrill Lynch downgraded Corning to accumulate from buy and Salomon Smith Barney cut it to outperform from buy.