GetOpenFileName API intermittently slow on 2003 server

Question

When running the code below on windows server 2003, there are intermittent slowdowns while GetOpenFileName common dialog initializes. the startup time varies at around ~30 seconds. The code below is a scratch program I made to exemplify the problem I'm having in my larger project but the problem exists in both.

One important note, is that when the network interfaces are all disabled, the time taken to initialize is much closer to normal - typically ~2 seconds. As soon as they are enabled again, the problem returns.

I have put the initialization time up against other programs with file open common dialogs (like Notepad) which do not have the same problem, with or without the network interfaces enabled.

Code:

getNewFileName.h:

#define _tWinMain wWinMain

#include "windows.h"
#include <string>
#include "resource.h"
using std::wstring;

#define ISOLATION_AWARE_ENABLED 1
#if defined _M_IX86
#pragma comment(linker,"/manifestdependency:\"type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='X86' publicKeyToken='6595b64144ccf1df' language='*'\"")
#elif defined _M_IA64
#pragma comment(linker,"/manifestdependency:\"type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='ia64' publicKeyToken='6595b64144ccf1df' language='*'\"")
#elif defined _M_X64
#pragma comment(linker,"/manifestdependency:\"type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='amd64' publicKeyToken='6595b64144ccf1df' language='*'\"")
#else
#pragma comment(linker,"/manifestdependency:\"type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")
#endif 

getNewFileName.cpp:

#include "getNewFileName.h"

HINSTANCE           hInst;
BOOL                InitInstance(HINSTANCE);
HWND                hWnd;
wstring             lastfile;
BOOL                getNewFileName(HWND owner, wstring title, wstring defaultfile, LPWSTR filetypes, OPENFILENAME &ofn, wstring lastdir, wstring lastfile, int mode, wstring extension);

int APIENTRY _tWinMain(HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    LPTSTR    lpCmdLine,
    int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    MSG msg;
    HACCEL hAccelTable;

    if (!InitInstance (hInstance))
    {
        return FALSE;
    }

    hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDR_ACCELERATOR1));

    // Main message loop:
    while (GetMessage(&msg, NULL, 0, 0))
    {
        if (!TranslateAccelerator(hWnd, hAccelTable, &msg))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    return (int) msg.wParam;
}

BOOL InitInstance(HINSTANCE hInstance)
{
    hInst = hInstance;
    OPENFILENAME ofn;
    wstring newfn;
    hWnd = CreateWindow(NULL, L"test", NULL,
        0, 0, 0, 0, NULL, NULL, hInst, NULL);
    BOOL ret = getNewFileName(hWnd, L"test", L"*.xml", L"XML Files\0*.xml\0", ofn, L"C:\\", lastfile, 1, L"xml");
    if (ret) { 
        newfn = ofn.lpstrFile;
        MessageBox(hWnd,newfn.c_str(),L"test",MB_OK);
    }
    ExitProcess(0);
    return TRUE;
}

void addPrefix(wstring &path) {
    wstring test = path.substr(0,4);
    if (path.substr(0,8) == L"\\\\?\\UNC\\" || path.substr(0,4) == L"\\\\?\\") { return; }
    wstring prefix = path.substr(0,2);
    if (prefix.compare(L"\\\\") == 0) { path.assign(L"\\\\?\\UNC\\"+path.substr(2,wstring::npos)); } else { path.assign(L"\\\\?\\"+path); }
    return;
}

UINT_PTR CALLBACK OFNHookProc(HWND hdlg, UINT uiMsg, WPARAM wParam, LPARAM lParam) {
    HICON hIcon;
    int width, height, xLeft, yTop;
    RECT rectToCenterOn, rectSubDialog;
    switch (uiMsg) {
    case WM_INITDIALOG:
        hIcon = LoadIcon(hInst, MAKEINTRESOURCE(IDI_PMMICO));
        SendMessage(GetParent(hdlg), WM_SETICON, ICON_BIG, (LPARAM)hIcon); 
        SendMessage(GetParent(hdlg), WM_SETICON, ICON_SMALL, (LPARAM)hIcon); 
        GetWindowRect(GetDesktopWindow(), &rectToCenterOn);
        GetWindowRect(GetParent(hdlg), &rectSubDialog);
        width = rectSubDialog.right-rectSubDialog.left;
        height = rectSubDialog.bottom-rectSubDialog.top;
        xLeft = rectToCenterOn.right / 2 - 
            (width) / 2;
        yTop = rectToCenterOn.bottom / 2 - 
            (height) / 2;
        BOOL test  = SetWindowPos(GetParent(hdlg), NULL, xLeft, yTop, width, height, SWP_NOSIZE);
        return (INT_PTR)FALSE;
        break;
    }
    return (INT_PTR)FALSE;
}

BOOL getNewFileName(HWND owner, wstring title, wstring defaultfile, LPWSTR filetypes, OPENFILENAME &ofn, wstring lastdir, wstring lastfile, int mode, wstring extension) {
    wstring lastdir_pre(lastdir);
    addPrefix(lastdir_pre);
    if (lastfile.compare(L"") == 0) { lastfile = defaultfile; }
    BOOL ret = false;
    wchar_t Buffer[30000];
    ofn.lStructSize = sizeof(OPENFILENAME);
    ofn.hwndOwner = owner;
    ofn.lpstrFile = Buffer;
    lastfile.copy(ofn.lpstrFile,lastfile.size(),0);
    ofn.lpstrFile[lastfile.size()] = '\0';
    ofn.nMaxFile = 30000;
    ofn.Flags = OFN_OVERWRITEPROMPT | OFN_ENABLEHOOK | OFN_EXPLORER;
    ofn.lpfnHook = OFNHookProc;
    ofn.lpstrFilter = filetypes;
    ofn.lpstrCustomFilter = NULL;
    ofn.nFilterIndex = 0;
    ofn.lpstrInitialDir = lastdir_pre.c_str();
    ofn.lpstrFileTitle = NULL;
    ofn.lpstrDefExt = extension.c_str();
    ofn.lpstrTitle = title.c_str();
    if (mode == 1) {
        ofn.Flags = ofn.Flags | OFN_PATHMUSTEXIST;
        ret = GetOpenFileName(&ofn); 
    } else if (mode == 2) {
        ret = GetSaveFileName(&ofn); 
    }
    if (ret == false) { ofn.lpstrFile[0] = '\0'; }
    return ret;
}