Gateway Computers yesterday warned of a much wider than expected third-quarter loss, saying that the Sept .11 attacks had hurt demand.Gateway issued its 900 Dublin-based workers with redundancy notices in August, and said it would close it's Dublin headquarters by the end of the fourth fiscal quarter of 2001. San Diego-based Gateway said it would take an additional charge of between $100-$130 million in the third quarter to write down the value of equity investments. It expected a loss of 14-17 cents a share, excluding special charges, in the third quarter, a far greater loss than analysts estimates. It closed at $4.85 on the New York Stock Exchange up 15 US cents.