This question may be related to a resolved thread.
I seem to have lost all the jquery ui styles in the CP after an upgrade to 2.3.1 (http://cl.ly/DAAa) - this is despite having done a straight replace of the base EE install themes folder.
Look at my view source, I can’t see any reference to the jquery-ui css file (jquery-ui-1.8.16.custom.css) - how can this be?