yo :: Integer -> [S s] -> S s
yo k (x1:x2:x3:x4:x5:[]) = a k x1 x2 x3 x4 x5

and with that the new run is

run' k = runST (yo k (map return [1 (-1) (-1) 1 0]))

(instead of the original where the list argument is laid out as
curried individuals).

where type S s = ST s Integer

-----

The compiler complains that:

    No instance for (Num (a -> a1 -> t -> t1 -> Integer))
      arising from the literal `1'
      at /Users/dauclair/projects/haskell/eclipse/Tasty/src/
ManOrBoy.hs:25:34-48
    Possible fix:
      add an instance declaration for
      (Num (a -> a1 -> t -> t1 -> Integer))
    In the expression: 1 (- 1) (- 1) 1 0
    In the second argument of `map', namely `[1 (- 1) (- 1) 1 0]'
    In the second argument of `yo', namely
        `(map return [1 (- 1) (- 1) 1 0])'

-----

So, how is it that a list of the lifted integers is different than
individually lifted integers, type-wise?  How can the list elements be
properly lifted to their stateful equivalents?  I'm using ghc-6.6.1