Ok the error is probably that there is an image missing, since now firebug refers to:
c2runtime.js (line 5783)
of the function
myx - (this.hotspotX * this.width),
myy - (this.hotspotY * this.height),
that draws the textures/images in the canvas.
The bug happens
around here and looks like :
So a missing image/texture (on the server) around here. Check in your project what you try to display when we are close to this ladder and that is missing on dropbox.
Maybe your chrome stored the texture in cache, but it wasn't uploaded/exported to the hosted project.