Can't get exact solution. Why ?

I'm using Compaq Visual fortran 6.1 (window XP platform)

My problem is simple

I hope to solve x of A*x = b

A = [ 4 2 0 0 0 0 ;
2 4 2 0 0 0 ;
0 2 4 2 0 0 ;
0 0 2 4 2 0 ;
0 0 0 2 4 2 ;
0 0 0 0 2 4 ] --> symmetric

b = [1;1;1;1;1;1]

In matCAD. I can get solution
x =
0.214
0.071
0.143
0.143
0.071
0.214

BUT !!, when I used sparse solver DSSKYD in compaq fortran CXML, I get
strange result agian and agian...
x =
0.2198413
0.0603175
0.1595238
0.1206349
0.1190476
0.1904762

I set as following in code

:
:
PARAMETER IDEBUG = 7
PARAMETER NMAX = 1000
PARAMETER NMAX_SKY = 11000
PARAMETER NSIZE = 6

INTEGER(4) N
INTEGER(4) IAUDIAG(NMAX)
INTEGER(4) NAU
INTEGER(4) LDBX
INTEGER(4) NBX
INTEGER(4) IPARAM(100)
INTEGER(4) IWRK
INTEGER(4) IERROR

REAL(8) AU(NMAX_SKY)
REAL(8) RPARAM(100)
REAL(8) RWRK
:
:
REAL(8) A(NSIZE,NSIZE), BX(NSIZE)
:
:
! CONSTRUCT [A], [BX]
DO I=1,NSIZE
A(I,I) = 4.
BX(I) = 1.
ENDDO

DO I = 1, (NSIZE-1)
A(I,I+1) = 2.
A(I+1,I) = 2.
ENDDO
:
:
CALL CONVERT_TO_SKYLINE(A,AU,IAUDIAG,NAU)

! parameters

N = NSIZE
LDBX = NMAX
NBX = 1

IPARAM(1) = 100
IPARAM(2) = 1200
IPARAM(3) = 2*N
IPARAM(4) = 0
IPARAM(5) = IDEBUG
IPARAM(6) = 2
IPARAM(7) = 1
IPARAM(8) = 1
IPARAM(9) = 0
IPARAM(10) = 1

RPARAM(1) = 1.D-12

IWRK = IPARAM(3)
RWRK = 0.

CALL DSSKYD(N,AU,IAUDIAG,NAU, BX,LDBX,NBX, IPARAM,RPARAM,
IWRK,RWRK,IERROR)


:
:

SUBROUTINE CONVERT_TO_SKYLINE(A,AU,IAUDIAG,NAU)

REAL(8),INTENT(IN)::A(:,:)
REAL(8),INTENT(OUT)::AU(:)
INTEGER(4),INTENT(OUT)::IAUDIAG(:)
INTEGER(4),INTENT(OUT)::NAU

INTEGER LOC,COUNTER

DO I=1,NSIZE

! SEARCH NON-ZERO VALUE
DO J=1,I
! IF NON ZERO VALUE FOUND, EXIT
IF (A(J,I)<>0) THEN
LOC = J
GO TO 10
ENDIF

ENDDO

10 DO J=LOC,I
NAU = NAU + 1
COUNTER = COUNTER + 1
AU(COUNTER) = A(J,I)
ENDDO
IAUDIAG(I) = COUNTER

END DO

END SUBROUTINE

**********************************************

I can't find mistake here
Could you find the mistake in this code ?
Thank you in advance

.