directx10 user input

[Sykes]

hi, this is my first post in these forums, im also quite new to programming so dont hate please just looking for some help with my direct x code that im trying to sort out. i am attempting to get user input working for the keyboard within my program the only problem im having at the moment is the error

Unhandled exception at 0x01372146 in GameEng_Main.exe: 0xC0000005: Access violation reading location 0x00000000.

which is then taking me to the line of

result = m_directInput->CreateDevice(GUID_SysKeyboard, &m_keyboard, NULL);

the code for the actual project is:

#include "UserInput.h"



InputClass::InputClass()
{
	m_directInput = 0;
	m_keyboard = 0;
}


InputClass::InputClass(const InputClass& other)
{
}

InputClass::~InputClass()
{
}

bool InputClass::Initialize(HINSTANCE hinstance, HWND hwnd)
{
	HRESULT result;

	//initialise the input interface
	result = DirectInput8Create(hinstance, DIRECTINPUT_VERSION, IID_IDirectInput8, (void**)&m_directInput, NULL);
	if(!result)
	{
		return false;
	}
	
	//create the device for the keyboard input 
 	result = m_directInput->CreateDevice(GUID_SysKeyboard, &m_keyboard, NULL);
	if(!result)
	{
		return false;
	}

	//set the data format - because its the keyboard can set to predefined data format
	result = m_keyboard->SetDataFormat(&c_dfDIKeyboard);
	if(!result)
	{
		return false;
	}

	//set the cooperative level for the keyboard so it doesnt comunicate with anything else
	result = m_keyboard->SetCooperativeLevel(hwnd, DISCL_FOREGROUND | DISCL_EXCLUSIVE);
	if(!result)
	{
		return false;
	}

	// Now acquire the keyboard.
	result = m_keyboard->Acquire();
	if(!result)
	{
		return false;
	}

}

void InputClass::Shutdown()
{

	//release the keyboard
	if(m_keyboard)
	{
		m_keyboard->Unacquire();
		m_keyboard->Release();
		m_keyboard = 0;
	}

	//release the main interface
	if(m_directInput)
	{
		m_directInput->Release();
		m_directInput = 0;
	}

	return;

}


bool InputClass::Frame()
{
	bool result;

	//read the state of the keyboard
	result = ReadKeyboard();
	if(!result)
	{
		return false;
	}

	//ProcessInput();

	return true;
}

bool InputClass::ReadKeyboard()
{
	HRESULT result;

	// Read the keyboard device.
	result = m_keyboard->GetDeviceState(sizeof(m_keyboardState), (LPVOID)&m_keyboardState);
	if(FAILED(result))
	{
		// If the keyboard lost focus or was not acquired then try to get control back.
		if((result == DIERR_INPUTLOST) || (result == DIERR_NOTACQUIRED))
		{
			m_keyboard->Acquire();
		}
		else
		{
			return false;
		}
	}
		
	return true;

}

bool InputClass::IsEscapePressed()
{
	// Do a bitwise and on the keyboard state to check if the escape key is currently being pressed.
	if(m_keyboardState[DIK_ESCAPE] & 0x80)
	{
		return true;
	}

	return false;
}