Let me describe the issue more clearly:
There are two identical red boxes in the same position.
Both are invisible before animation starts.
First box is showing for 60 frames then in onComplete function it becomes visible false.
Second box has delay 60 frames.
The problem is that there is a blank frame between this two Tweens.
http://jsfiddle.net/onlymega/ALJJG/3/
How this can be fixed?
TweenMax.to(item, 60, { useFrames: true, visibility:'visible', onComplete: onCompleteFunc});
TweenMax.to(item2, 60, { delay:60, useFrames: true, visibility:'visible'});
function onCompleteFunc(){
item.style.visibility = "hidden";
}