C / C++ / MFC

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
	DialogBox(hInstance, MAKEINTRESOURCE(101), NULL, DialogProc);
	MSG msg;
	while (GetMessage(&msg, NULL, 0, 0) != 0)
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return (int)msg.wParam;
}

INT_PTR CALLBACK DialogProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
HDC hdc; PAINTSTRUCT ps;
switch (message) {
	case WM_COMMAND:
		switch(LOWORD(wParam)) {
			case IDSAVE:
				OPENFILENAME OFN;
				OFN.hwndOwner = hWnd;
				[...]
				//PROBLEM IS HERE. The save file dialog is half-frozen and never returns.
				if (GetSaveFileName(&OFN)) {[...]}
				break;
			default:
				return DefWindowProc(hWnd, message, wParam, lParam);
		}
		return true;
	case WM_PAINT:
		hdc = BeginPaint(hWnd, &ps);
		EndPaint(hWnd, &ps);
		break;
	case WM_INITDIALOG:
		[...]
		return true;
	case WM_CLOSE:
		[...]
		return true;
	case WM_DESTROY:
		[...]
		return true;
	default:
		return DefWindowProc(hWnd, message, wParam, lParam);
	}
	return false;
}