handles not a struct in figure_OutputFcn

Whenever I uncomment the call to uiwait in a figure's OpeningFcn, the one GUIDE generates, I always get an error message in the figure's OutputFcn stating that handles is not a structure. How is this supposed to work?

% --- Executes just before PreferencesMenu is made visible.
function PreferencesMenu_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to PreferencesMenu (see VARARGIN)

% Choose default command line output for PreferencesMenu
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

% UIWAIT makes PreferencesMenu wait for user response (see UIRESUME)
uiwait(handles.figure1);

% --- Outputs from this function are returned to the command line.
function varargout = PreferencesMenu_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;
disp('Here I am')

Note, If I leave the call to uiwait commented out, then I don't get the error and I do see the output of the disp call. What is going on here?

Thanks a bunch, Bill