WoW Freezes on Training?

Running any addons, Concise?

This sounds like something is either misbehaving or just conflicting.

I'd try this after full and proper reset UI and before re-adding anything you may have running as a first trouble-shooting step. As a Mac user, you'll want that link.

To do a full reset UI, you will want to save your addons in another spot if you wish to preserve them.

Then rename/delete or move your WTF, Cache and Interface folders while WoW is shutdown. Reboot your system.

Note, if you are running Vista make sure your permissions are set so it does not undo your changes.

More detailed instructions for different operating systems, including Macs are here.

http://us.blizzard.com/support/article.xml?articleId=18761&searchQuery=reset%20UI&pageNumber=1

Q u o t e:
I've been having the same issue for a few months - I have removed the interface folder, cleared WTF and Cache and it works fine - clearly it's an addon - but which one?

So far, I'm narrowing my problem down to Carbonite, DBM, Auctioneer, Bagnon, Quartz etc - Recount, when uninstalled still resulted with the same issue :\

*sigh*

Well in the thread above (which is a couple months old, btw) - they were saying it was likely Recount.