The grainy 30-second commercials ... suggest a government cover-up of the Sept. 11, 2001, attacks. The advertisements, which ran repeatedly ... on several cable networks, including CNN, Fox News and ESPN, offer a Web site, an address and a phone number. The ads are the latest salvo from James W. Walter ... who over the years has financed programs promoting voter registration in low-income neighborhoods and prison reform. The television commercials, as well as ads in magazines and newspapers, including The New York Times, The Wall Street Journal and The Daily News, are part of a $3 million national campaign paid for by Mr. Walter in an effort to press for the reopening of the investigation by the independent Sept. 11 commission. We've never gotten solid answers on why Tower 7 collapsed when it was two full blocks away from where the planes hit," he said. "We've also never received an answer for how such a large plane left such a small hole in the side of the Pentagon." A Zogby poll of New Yorkers' opinions about the 9/11 investigation, released last month, indicated that 49 percent of New York City residents and 41 percent of New York state residents believed that some federal officials "knew in advance that attacks were planned on or around September 11, 2001, and that they consciously failed to act." The poll also found that 66 percent of New York City residents and 56 percent of state residents wanted a fuller investigation of the "still unanswered questions."