Why do wet get the "Can't vectorise expression GHC.Prim.Int#" error in DPH programs?

Question

I was trying to implement the nqueens problem using DPH but I ended up with the Can't vectorise GHC.Prim.Int# error. When I googled for the error I found a GHC Bug which talks about vectorizing literals used for pattern matching (http://haskell.1045720.n5.nabble.com/GHC-5702-Can-t-vectorise-pattern-matching-on-numeric-literals-td5076659.html). I am not sure if this is the same bug. My code is as follows,

{-# LANGUAGE ParallelArrays #-}
{-# OPTIONS_GHC -fvectorise #-}
module NQueensP (nqueens_wrapper) 
where

import qualified Prelude
import Data.Array.Parallel
import Data.Array.Parallel.Prelude
import Data.Array.Parallel.Prelude.Int as I
import qualified Data.Array.Parallel.PArray as P


isSafe i q n  = isSafeHelper i (Prelude.zip (P.toList (toPArrayP q)) [n, n I.- 1..1]) 
            where isSafeHelper i []  = True
                  isSafeHelper i (x:xs) = (i I.== Prelude.fst x) && I.abs(i I.-   
                                  (Prelude.fst x)) I./= I.abs(n I.- (Prelude.snd x)) && 
                                       isSafeHelper i xs

nqueens_wrapper::Int -> PArray (PArray Int)
nqueens_wrapper n = toPArrayP (mapP toPArrayP (nqueens n 0))

nqueens::Int -> Int -> [:[:Int:]:]
nqueens n 1 = [:[:i:] | i <- (enumFromToP 1 n) :]
nqueens n k = [: [:i:] +:+ q | i <- oneton, q <- boards, isSafe i q k:]
           where boards = nqueens n (k I.- 1)
                 oneton = (enumFromToP 1 n) 

Please let me know if I am doing something wrong. I am using GHC 7.4.1.

Thanks in advance.