I deleted : -
jquery-1.7.2.min.js
and
jquery-noconflict.js
From the mangeto installation folder js/ias/
As I saw there was an error / conflict being read when using Inspect Element on the category page. Maybe due to using AdBlockPlus. Very stupid of me anyway.
After I put the files back all javascript actions have ceased to operate on the category page however they still work elsewhere on the website.
I have tried flushing the cache and other things but functionality on the category page has not returned.
What can I do?