I had osx 10.7.4 (whatever was the lastest) and now 10.8 brand new osx and both
I repeat both work for me with kies and the siii
1. Load kies from website (uninstall all other versions of kies first like kies wifi from phone) Transfer, Sync & Manage Music, Movies, Photos, Contacts and Calendars with Kies
2. reboot computer
3. open up kies
4. Make sure phone is on and not locked.
5. Plug phone in to an empty USB port on the computer, not hub. (try one on the rear or a different one on the computer and even disconnect all unused hubs ect..)
6. now pull down on the phone the notification and touch the "connected as a camera or media..." this will bring up a choice
7. Whatever is the given chosen one at the moment choose the opposite then choose media device MTP as your last choice
so if media is listed then choose camera then choose media again and my computer after about 30 seconds to 60 seconds in kies shows up every time.
For the life of me I can not get my phone to work with windows (but not important since it works for me on my mac)
If if is still not working then you could have something loaded that is conflicting (like some other program, what it is I dont know, you will have to search) or ??
Best of luck to all, I don't know why these phones are soooooo picky, I am on verizon are you, it may be verizon locking them down so no root???? Just a thought.
EDIT: I had kies working on 10.7 then upgraded to 10.8, so kies continued to work
BUT on my macbook pro I tired to load kies on 10.8 and it does not connect to it, it just sits there saying connecting and never does. android file transfer does work fine on both, but that does not help the itunes transfer for you.