[jQuery] preventDefault() not working in FF?

[jQuery] preventDefault() not working in FF?


does anyone know why the preventDefault() would work fine in IE but
not in Firefox? I tired placing it elsewhere and putting it in
multiple plaves - no luck...
Thanks for any pointers!
isMouseDown = false;
$('#dragger').mousedown(function(e){
isMouseDown = true;
    $(document).mousemove(function(e){
        e.preventDefault(); // this bit for some reason is not taken
seriously by Firefox
        if(isMouseDown == true){
            // move things...
        }
    });
}).mouseup(function(e){
isMouseDown = false;
});