In looking over the league schedule, there are four losses that are sinking the ACC in the computers. And remember, the computers do not account for margin of victory, so Maryland's 1-point escape over William & Mary, and Wake Forest's 3-point win over Liberty really do not count against the conference. And Miami getting its doors blown off by Kansas State and Notre Dame doesn't really hurt more than a one-point loss would.
These four stand out from the rest.
North Carolina State 21, Tennessee 35: Tennessee is 0-7 in the SEC. Zero and seven. The Kentucky game could change that this weekend. But as of now, Tennessee's three other wins are over Georgia State, Akron and Troy. Certainly Tennessee is not as awful as its record (losses to Georgia, South Carolina and Missouri were by an average of 4 points), but the computers only see wins and losses.
Middle Tennessee 49, Georgia Tech 28: Georgia Tech has improved a lot since this point, but this loss still happened. Middle Tennessee state is not horrible. It's 7-3 on the year. But... it lost to McNeese State. That's an FCS (D1-AA) school. The ACC's Coastal Division champ, which has a shot to go to the Orange Bowl, lost to a school that lost to an FCS team. At home. Yup.
Boston College 31, Army 34: Army is 2-9 on the season. It lost to Stony Brook! Another ACC team losing to a squad that lost to a school from the FCS (D1-AA). Boston College sets the ACC's bottom, and this loss makes the ACC's bottom really low.
Virginia Tech 17, Pitt 35: This one hurt a lot. Virginia Tech, with eight returning starters on defense, was being counted on to carry the Coastal Division. Instead, it lost to Pitt, which not only has six losses, but one of those came courtesy of an FCS (D1-AA) in Youngstown State! Consider Pitt's wins for a moment: Virginia Tech, Gardner-Webb, Buffalo and Temple. That makes Virginia Tech appear really bad in the computers.
Oh, and there's also the issue of a lack of marquee non-conference wins. But that's for another day.