Shares of Acer stock were down nearly 7% on the Taiwan Stock Exchange Tuesday on news that the PC manufacturer had unexpectedly and significantly lowered it’s first-quarter sales estimates. The PC maker had previously estimated its first-quarter PC sales would grow 3% from the previous quarter. Now, Acer has adjusted its forecast, saying it expects sales to drop 10% compared to the prior quarter. Asustek, an Acer competitor, is also struggling with similar sales declines in the first quarter. Acer cite...