IndexBuffer Blues

I am trying to write a simple terrain engine (which is turning out to be not so simple). I've got most of the code down (C#/DX9), but when it comes to drawing the result on the screen, it fails when I try to set the device's indexbuffer. Here is my source code:

//1) Clear the back buffer

device.Clear(ClearFlags.Target | ClearFlags.ZBuffer, clClear, 1.0F, 0);

//2) indicate that we are ready to being drawing to the back buffer

device.BeginScene();

//3) draw scene -- actual rendering goes here

if(bmpHeightMap != target.bmpHeightMap)
{//if a new heightmap has been loaded on the main form, load it here too

	bmpHeightMap = target.bmpHeightMap;
	
	//create a vertex/index buffer

	int nBmpWidth = bmpHeightMap.Width;
	int nBmpHeight = bmpHeightMap.Height;
	int nTop = (nBmpHeight / -2) * 20;
	int nLeft = (nBmpWidth / -2) * 20;
	Color clPixel = Color.Black;
	CustomVertex.PositionColored[] vertices =
			new CustomVertex.PositionColored[nBmpWidth * nBmpHeight];
	int[] nIndices = new int[(6 * (nBmpWidth - 1) * (nBmpHeight - 1))];
	
	
	for(int i = 0; i < nBmpWidth; i++)
	{//create the vertices for the vertex buffer

		for(int j = 0; j < nBmpHeight; j++)
		{
			clPixel = bmpHeightMap.GetPixel(i,j);
			vertices[nCount++] = new CustomVertex.PositionColored(
								nLeft + (i * 20),
								nTop + (j * 20),
								clPixel.R * 5, Color.Green.ToArgb());
		}
	}

	nCount = 0;
	
	for(int i = 0; i < nBmpHeight * nBmpWidth; i += nBmpWidth)
	{//create the indices for the index buffer

		if(i != (nBmpWidth * (nBmpHeight - 1)))
		{
			for(int j = 0; j < nBmpWidth - 1; j++)
			{
				nIndices[nCount++] = i + j;					//A1

				nIndices[nCount++] = i + j + 1;				//A2

				nIndices[nCount++] = i + j + nBmpWidth;		//B1

				nIndices[nCount++] = i + j + 1;				//A2

				nIndices[nCount++] = i + j + nBmpWidth + 1;	//B2

				nIndices[nCount++] = i + j + nBmpWidth;		//B1

			}
		}
	}
	ibTerrain = new IndexBuffer(typeof(int), (int)nCount, device, 0, Pool.Default);
	vbTerrain = new VertexBuffer(typeof(CustomVertex.PositionColored), vertices.Length,
									device, 0, CustomVertex.PositionColored.Format,
									Pool.Default);
	//write values for index buffer

	GraphicsStream stmIB = ibTerrain.Lock(0,0,0);
	stmIB.Write(nIndices);
//						ibTerrain.SetData(nIndices, 0, 0);

	ibTerrain.Unlock();
	
	//write values for vertex buffer

	GraphicsStream stmVB = vbTerrain.Lock(0,0,0);
	stmVB.Write(vertices);
	vbTerrain.Unlock();
	
	//set camera to look at map from a distance


	clClear = Color.Black;
}
if(bmpHeightMap != null)
{//don't draw anything if a heightmap hasn't been loaded. otherwise, draw it!

	//draw the heightmap

	device.VertexFormat = CustomVertex.PositionColored.Format;
	device.SetStreamSource(0, vbTerrain, 0, VertexInformation.GetFormatSize(CustomVertex.PositionColored.Format));
	device.RenderState.FillMode = FillMode.Solid;
	device.Indices = ibTerrain;
	device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, (int)nCount, 0, (int)nCount / 6);
}
//4) indicate that we are done drawing to the back buffer

device.EndScene();

//5) Copy back buffer to the display

device.Present();

It doesn't throw an error until the "device.Indices = ibTerrain;". I looked at the SDK "fractal" example and the index buffer part is almost identical. What could possibly be wrong?? PS: Does anyone know why for the last few days GameDev.net's server is down more often than not? [edited by - langguy on August 12, 2003 5:06:35 PM]