Dialog - position: 'center' - Issue

Dialog - position: 'center' - Issue


When I create a dialog box using "position: 'center' " the box is
placed in the vertical center of the html height instead of the center
of the window height. The same problem does not occur on the examples
page at: http://dev.jquery.com/view/trunk/plugins/ui/tests/dialog.html
and I cannot find an appreciable difference. Is this a known problem?
Perhaps a problem with my styles?
Thanks in advance for your help.
-R.A. Ray
I am using core v. 1.2.1, UI v. 1.0
My code:
$('#dialogBox').dialog(
    {
        resize: false,
        width: 400,
        height: 150,
        position: 'center',
        shadow: true,
        buttons:
        {
            'Ok': function()
            {
                window.location = action;
            },
            'Cancel': function()
            {
                $( 'div.ui-dialog' ).remove();
                $( 'div.ui-shadow' ).remove();
                $( overlay ).remove();
                $( 'body' ).removeClass( 'admin' );
            }
        }
    }
);