Reference Error #1065 problem

programming flash
1

I realise theres already been a tonne of threads about this error, but none of them seem to be much help in this case.
I keep getting this error

ReferenceError: Error #1065: Variable vo::desc is not defined.
at model::VideoModel/showThumb()
at views::VideoLink/_rollOver()

Here is the code for the videomodel show thumb function

public function showThumb( vo:VideoVO ):void {

    var i:int;
    for (i = 0; i < thumbs.length; i++) {
        if (thumbs*.vo==vo) {
            TweenMax.to( thumbs[ i ], 0, { autoAlpha: 1 } );
        } else {
            TweenMax.to( thumbs[ i ], 0, { autoAlpha: 0 } );

        }
    }

    docClass.videoLabel.text=vo?vo.desc:currItem?currItem.desc:'';
}

Anyone got any ideas whats going on here?
Thanks