[ODE] Trimesh collisions

[join at krakendev.com]

I'm currently attempting to get up to speed on how TriMeshes are
implemented in ODE, and I've made some progress. At present, however, I
can't seem to get the trimesh I'm working with to collide with the ground.
It's a simple diamond shaped mesh to which I've attached a 'box' body as
such:

static dGeomID ground;

static dGeomID TriMesh;
static dTriMeshDataID TriMeshData;
static dBodyID TriBody;

dMass m;

    // create world

    world = dWorldCreate();
    space = dHashSpaceCreate (0);
    contactgroup = dJointGroupCreate (0);
    dWorldSetGravity(world,0.0,-1.0,0.0);
    ground = dCreatePlane (space,0,.5,0,0);

    TriMeshData = dGeomTriMeshDataCreate();

    dGeomTriMeshDataBuildSimple(TriMeshData,
         (dReal*)loader->v,loader->numVerts,
                 loader->i,loader->numIndices);
    TriMesh = dCreateTriMesh(space, TriMeshData, 0, 0, 0);
    dGeomSetPosition(TriMesh,0.0,1.0,0.0);
    dGeomSetData(TriMesh,TriMeshData);

    TriBody = dBodyCreate (world);
     //                 w, h , depth
    dMassSetBox (&m,1,0.15,0.8,0.25);
    dMassAdjust (&m,1.0);
    dBodySetPosition(TriBody, 0.0, 1.0, 0.0);
    dBodySetMass (TriBody,&m);

    dGeomSetBody (TriMesh,TriBody);

However, the 'diamond' just cruises through the ground, where the boxes I
had created earlier landed. My collision callback is near verbatim from
the buggy example:

static void nearCallback (void *data, dGeomID o1, dGeomID o2)
{

  int i,n;

  const int N = 10;
  dContact contact[N];
  n = dCollide (o1,o2,N,&contact[0].geom,sizeof(dContact));
  if (n > 0) {
    for (i=0; i<n; i++) {
      contact[i].surface.mode = dContactSlip1 | dContactSlip2 |
	dContactSoftERP | dContactSoftCFM | dContactApprox1;
      contact[i].surface.mu = dInfinity;
      contact[i].surface.slip1 = 0.1;
      contact[i].surface.slip2 = 0.1;
      contact[i].surface.soft_erp = 0.5;
      contact[i].surface.soft_cfm = 0.3;
      dJointID c = dJointCreateContact (world,contactgroup,&contact[i]);
      dJointAttach (c,
		    dGeomGetBody(contact[i].geom.g1),
		    dGeomGetBody(contact[i].geom.g2));
    }
  }
}

Thanks in advance for any help.