That .dll is not part of CS6, but is probably associated with iTunes or some other Apple software you have running, or possibly a font manager if you use one.
Thanks for the reply. I uninstalled/reinstalled all the Apple stuff including iTunes, Quicktime and also the font manager, but I'm still getting the annoying message. I appreciate you trying to help.
With a bit more searching I found the source of the problem. For anyone interested it's explained here
I tried to install a trial of Extensis Suitcase last week but for some reason it failed to install. It was after that I started noticing the error message, but because Suitcase had failed to load I didn't connect the two events! After reading the above thread implicating Suitcase, I looked in the InDesign plugins folder and, lo and behold, a folder called Font Activation that contained Extensis files! I moved them out and the error message is gone!
Thanks again to P Spier and thanks to Adobe for these forums.