I'm reviewing this, and doing a little debugging in firebug at the same time.
I am also prebuffering a megavideo at the same time. (it seems to slow down my FF a bit)
When launching the preview in firefox, the cloud1 and cloud3 don't wrap on their very first roll.
Checking line 55 in wrap_behavior.js, it seems that every tick the bounding box right edge is less than 0.
(current value : -0.9279989999896685)
Then, each tick, the following lines are executed, making the object move left, outside of screen instead of moving right.
Maybe instead of
l.57: this.inst.x = layout.width - this.inst.x;
=> this.inst.x = layout.width - this.inst.width/2;
=> this.inst.x = int(layout.width - this.inst.x);
would work better (having a true 0).