DirectX9中的访问冲突

最简单的说法是:我的代码每次运行时都会抛出访问冲突错误。我已经得出结论，这是在函数System::renderFrame()中调用this->d3ddev.(whatever)的错误。这个函数从第112行开始。如果有人能帮我一下，那就太好了。(顺便说一下，我已经让它工作了，但是我想把这些代码放入类中，这就是我开始遇到麻烦的地方。另外，我之前被告知要确保初始化所有指针。它们通过d3d->createDevice()

system.h

#ifndef SYSTEM_H
#define SYSTEM_H
#include "stdinc.h"

class System {
  private:
    void initD3D (void);
    void cleanD3D (void);
    void setUpHWND (HINSTANCE, LPSTR, int);
    static LRESULT CALLBACK StaticWindowProc(HWND, UINT, WPARAM, LPARAM);
    LRESULT WindowProc(HWND, UINT, WPARAM, LPARAM);
    HWND window;
    WNDCLASSEX windowClass;
    LPDIRECT3D9 d3d;
    LPDIRECT3DDEVICE9 d3ddev;
    D3DPRESENT_PARAMETERS d3dpp;
    HINSTANCE hInstance;
    LPSTR lpCmdLine;
    int nCmdShow;
  public:
    System (void);
    System (HINSTANCE, LPSTR, int);
    System (const System&);
    ~System (void);
    void renderFrame (void);
};
#endif

system.cpp

#include "system.h"
//////////////////////////////////////////////////
// Class: System
// Private
//////////////////////////////////////////////////
void System::initD3D (void) {
    this->d3d = Direct3DCreate9(D3D_SDK_VERSION);
    ZeroMemory(&(this->d3dpp), sizeof(d3dpp));
    this->d3dpp.Windowed = WINDOWED;
    this->d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
    this->d3dpp.hDeviceWindow = this->window;
    this->d3dpp.BackBufferFormat = D3DFMT_X8R8G8B8;
    this->d3dpp.BackBufferWidth = SCREEN_WIDTH;
    this->d3dpp.BackBufferHeight = SCREEN_HEIGHT;
    this->d3dpp.EnableAutoDepthStencil = TRUE;
    this->d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
    this->d3d->CreateDevice(D3DADAPTER_DEFAULT,
        D3DDEVTYPE_HAL,
        this->window,
        D3DCREATE_SOFTWARE_VERTEXPROCESSING,
        &(this->d3dpp),
        &(this->d3ddev));
    this->d3ddev->SetRenderState(D3DRS_LIGHTING, FALSE);
    this->d3ddev->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
    this->d3ddev->SetRenderState(D3DRS_ZENABLE, TRUE);
};
void System::cleanD3D (void) { 
    this->d3d->Release();
    this->d3ddev->Release();
};
void System::setUpHWND (
                        HINSTANCE hInstance,
                        LPSTR lpCmdLine,
                        int nCmdShow) {
    this->hInstance = hInstance;
    this->lpCmdLine = lpCmdLine;
    this->nCmdShow = nCmdShow;
    ZeroMemory(&(this->windowClass), sizeof(WNDCLASSEX));
    this->windowClass.cbSize = sizeof(WNDCLASSEX);
    this->windowClass.style = CS_HREDRAW | CS_VREDRAW;
    this->windowClass.lpfnWndProc = System::StaticWindowProc;
    this->windowClass.hInstance = this->hInstance;
    this->windowClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    this->windowClass.lpszClassName = "WindowClass";
    RegisterClassEx(&(this->windowClass));
    this->window = CreateWindowEx(NULL, "WindowClass", "The Direct3D Program", 
        WS_OVERLAPPEDWINDOW, SCREEN_X, SCREEN_Y, SCREEN_WIDTH, SCREEN_HEIGHT,
        NULL, NULL, this->hInstance, NULL);
};
LRESULT CALLBACK System::StaticWindowProc (HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
    System *SystemPtr = (System*)GetWindowLong(hWnd, GWLP_USERDATA);
    if(SystemPtr)
    {
        return SystemPtr->WindowProc(hWnd, message, wParam, lParam);
    }
    else
    {
       return DefWindowProc(hWnd, message, wParam, lParam);
    }
};
LRESULT System::WindowProc (HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
    switch(message)
    {
    case WM_DESTROY:
        {
            PostQuitMessage(0);
            return 0;
        } break;
    }
    return DefWindowProc(hWnd, message, wParam, lParam);
};
//////////////////////////////////////////////////
// Class: System
// Public
//////////////////////////////////////////////////
System::System (void) {
};
System::System (
                HINSTANCE hInstance,
                LPSTR lpCmdLine,
                int nCmdShow) {
    this->setUpHWND(hInstance, lpCmdLine, nCmdShow);
    ShowWindow(this->window, this->nCmdShow);
    this->initD3D();
};
System::System (const System &) {
};
System::~System (void) {
    this->cleanD3D();
};
void System::renderFrame (void) {
    // Update the camera here
    // Update objects
    // Clear objects
    // FOR SOME REASON THERE IS AN ERROR HERE
    this->d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 255, 0), 1.0f, 0);
    this->d3ddev->Clear(0, NULL, D3DCLEAR_ZBUFFER, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);
    this->d3ddev->BeginScene();
    // Draw objects
    // Finish up
    this->d3ddev->EndScene(); 
    this->d3ddev->Present(NULL, NULL, NULL, NULL); 
};

main.cpp

#include "system.h"
int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int nCmdShow) {
    System MainSys;
    MainSys = System(hInstance, lpCmdLine, nCmdShow);
    // Enter the main loop
    MSG msg;
    while (TRUE)
    {
        while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        if (msg.message == WM_QUIT)
            break;
        MainSys.renderFrame();
    }
    // Clean up DirectX and the COM
    //delete MainSys;
    return msg.wParam;
};