Jquery Colorbox arrows changes do not update

Greetings,

I have changed the appearance of the Colorbox navigation arrows by replacing a controls.png file in theme2 folder.
Alas they are not update, the old control.png image file seems to be taken in charge.

As far as I remember this is a very first time this happen.
I have purged all browser cache. The same results occurs in any machine and different browsers.

I will deeply appreciate any helpful suggestion.
Regards