Problem initializing DirectX

Hi, I have a problem when initializing DirectX. The code is as follows:

#include <Windows.h>
#include <WindowsX.h>
#include <D3D11.h>
#include <D3DX11.h>
#include <D3DX10.h>

#pragma comment (lib, "d3dx10.lib")

#define WINDOW_WIDTH 800
#define WINDOW_HEIGHT 600

//global declarations
IDXGISwapChain *swapChain;			//the pointer to the swap chain interface
ID3D11Device *device;				//the pointer to the Direct3D device interface
ID3D11DeviceContext *deviceContext;	//the pointer to the Direct3D device context
ID3D11RenderTargetView *backBuffer;	//the pointer to the back buffer

//function prototypes
void InitD3D(HWND hWnd);
void RenderFrame(void);
void CleanD3D(void);

//the message handler function prototype
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);

//the entry point for the Windows program
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
	HWND hWnd;		//handle to the window
	WNDCLASSEX wc;	//holds information for the window class

	ZeroMemory(&wc, sizeof(WNDCLASSEX)); // clear out the window class for use

	//fill in the window class struct with the needed information
	wc.cbSize = sizeof(WNDCLASSEX);
	wc.style = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc = WindowProc;
	wc.hInstance = hInstance;
	wc.hCursor = LoadCursor(NULL, IDC_ARROW);
	wc.hbrBackground = (HBRUSH)COLOR_WINDOW;
	wc.lpszClassName = L"WindowClass1";

	RegisterClassEx(&wc); //register the window class

	RECT wr = {0, 0, WINDOW_WIDTH, WINDOW_HEIGHT};		//set the size of the client area of the window
	AdjustWindowRect(&wr, WS_OVERLAPPEDWINDOW, FALSE);  //adjust the size

	hWnd = CreateWindowEx(NULL, 
						  L"WindowClass1",					//name of the window class
						  L"Our First Windowed Program",	//title of the window
						  WS_OVERLAPPEDWINDOW,				//window style
						  300,								//x-pos of the window
						  300,								//y-pos of the window
						  wr.right - wr.left,				//width of the window
						  wr.bottom - wr.top,				//height of the window
						  NULL,								//we have no parent window, NULL
						  NULL,								//we aren't using menus, NULL
						  hInstance,						//application handle
						  NULL);							//used with multiple windows, NULL

	ShowWindow(hWnd, nCmdShow); //display the window on the screen

	//ENTER THE MAIN LOOP:

	MSG msg; //holds Windows event messages

	//enter the infinite message loop
	while(TRUE)
	{
		//check to see if any messages are waiting in the queue
		if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
		{
			//translate keystroke messages into the right format
			TranslateMessage(&msg);
			//send the message to the WindowsProc function
			DispatchMessage(&msg);
			//check to see if it's time to quit
			if (msg.message == WM_QUIT)
				break;
		}
		else
		{
			RenderFrame();
		}
	}
}

//this is the main message handler for the program
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	//sort through and find what code to run for the message given
	switch (message)
	{
	case WM_DESTROY:
		{
			PostQuitMessage(0);
			return 0;
		} break;
	}

	//handle any messages the switch statement didn't
	return DefWindowProc(hWnd, message, wParam, lParam);
}

//this function initializes and prepares Direct3D for use
void InitD3D(HWND hWnd)
{
	DXGI_SWAP_CHAIN_DESC scd; //a struct holding information about the swap chain
	ZeroMemory(&scd, sizeof(DXGI_SWAP_CHAIN_DESC));

	//fill the swap chain description struct
	scd.BufferCount = 1;							    //one back buffer
	scd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;	//use 32-bit color
	scd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;	//use swap chain as a render target
	scd.OutputWindow = hWnd;							//the window to be used
	scd.SampleDesc.Count = 4;							//how many multisamples
	scd.Windowed = TRUE;								//windowed/full-screen mode

	//create a device, device context and swap chain using the information in the scd struct
	D3D11CreateDeviceAndSwapChain(NULL,
							      D3D_DRIVER_TYPE_HARDWARE,
								  NULL,
								  NULL,
								  NULL,
								  NULL,
								  D3D11_SDK_VERSION,
								  &scd,&swapChain,&device,
								  NULL,&deviceContext);

	//get the address of the back buffer
	ID3D11Texture2D *pBackBuffer;
	swapChain->GetBuffer(0, __uuidof(ID3D11Texture2D), (LPVOID*)&pBackBuffer);

	//use the back buffer address to create the render target
	device->CreateRenderTargetView(pBackBuffer, NULL, &backBuffer);
	pBackBuffer->Release();

	//set the render target as the back buffer
	deviceContext->OMSetRenderTargets(1, &backBuffer, NULL);

	//set the viewport
	D3D11_VIEWPORT viewport;
	ZeroMemory(&viewport, sizeof(D3D11_VIEWPORT));

	viewport.TopLeftX = 0;
	viewport.TopLeftY = 0;
	viewport.Width = WINDOW_WIDTH;
	viewport.Height = WINDOW_HEIGHT;
	deviceContext->RSSetViewports(1, &viewport);
}

//this function cleans up Direct3D and COM
void CleanD3D(void)
{
	//close and release all existing COM objects
	swapChain->Release();
	backBuffer->Release();
	device->Release();
	deviceContext->Release();
}

//this is the function used to render a single frame
void RenderFrame(void)
{
	//clear the back buffer to a deep blue
	deviceContext->ClearRenderTargetView(backBuffer, D3DXCOLOR(0.0f, 0.2f, 0.4f, 1.0f));

	//do 3D rendering on the back buffer here

	//switch the back buffer and the front buffer
	swapChain->Present(0, 0);
}

I get no compiler errors but when I lunch the program it crashes with the following exception:

Unhandled exception at 0x779f15de in DirectX_Test.exe: 0xC0000005: Access violation reading location 0x00000000.

When I remove the ClearRenderTargetView() function call in the RenderFrame() function the application wont crash. Any suggestions?

Best Regards
Robin