Icons are broken with 4.3 library

clear your browser cache

See http://ckeditor.com/forums/CKEditor/icons.png-not-cache-busted-on-upgrade and associated CKEditor ticket that seems to explain why this problem is occurring. In my case, the upgrade worked fine on my test Drupal system but failed on my production system. Clearing the browser cache did NOT resolve the problem. I am behind a caching server that was stubbornly serving up the old icons.png file (10794 bytes, kama version) instead of the new one (7792 bytes). Although a 'hard refresh' of a page normally causes the caching server to fetch a new version, this does not apply to all elements of the page. I ended up manually clearing icons.png from the caching server although it is possible that manually loading the icons.png file and then doing a 'hard refresh' would have worked as well.