CFD Online Discussion Forums - [blockMesh] mergePatchPairs Problems

I am trying to mesh the attached drawing. Below is my blockMeshDict file which is receiving a fatal error when I try to run blockMesh. The error says "point 10 already marked for removal" and I'm not sure what this means. Any help getting this to work would be appreciated.

Quote:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.1 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

//convertToMeters 0.1;

vertices
(
//front
(0 0 0) //0
(1 0 0)
(2 0 0)
(0 1 0)
(1 1 0)
(2 1 0)
(0 2 0)
(1 2 0)

(0 0 1)
(1 0 1)
(2 0 1)
(0 1 1)
(1 1 1)
(2 1 1)
(0 2 1)
(1 2 1)

(2 2 0)
(2 2 1)
(1 1.5 0)
(1 1.5 1)
(2 1.5 0)
(2 1.5 1)
);

blocks
(
hex (0 1 7 6 8 9 15 14) (10 20 1) simpleGrading (1 1 1)
hex (1 2 5 4 9 10 13 12) (10 10 1) simpleGrading (1 1 1)
hex (18 20 16 7 19 21 17 15) (10 10 1) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
inlet
{
type patch;
faces
(
(0 3 11 8)
(3 6 14 11)
);
}
outlet1
{
type patch;
faces
(
(2 5 13 10)
);
}
shell
{
type wall;
faces
(
(6 7 15 14)
(7 16 17 15)
(16 20 21 17)
(20 18 19 21)
(18 4 12 19)
(4 5 13 12)

(1 2 10 9)
(0 1 9 8)
);
}

frontAndBack
{
type empty;
faces
(
(0 1 7 6)
(1 2 5 4)
(8 9 15 14)
(9 10 13 12)

(18 20 16 7)
(19 21 17 15)
);
}
);

patches
(
patch slave
(
(1 7 15 9)
)

patch master1
(
(1 4 12 9)
)

patch master2
(
(18 7 15 19)
)
);

mergePatchPairs
(
(master1 slave)
(master2 slave)
);

// ************************************************** *********************** //