to be at sixes and sevens

from The Collaborative International Dictionary of English v.0.48

Six \Six\, n.
   1. The number greater by a unit than five; the sum of three
      and three; six units or objects.
      [1913 Webster]

   2. A symbol representing six units, as 6, vi., or VI.
      [1913 Webster]

   {To be at six and seven} or {To be at sixes and sevens},
      (a) to be in disorder. --Bacon. --Shak. --Swift.
      (b) to be in a dispute or disagreement; -- often used with
          with.
          [1913 Webster +PJC]