A Mac (and Windows, too, for that matter) can be set up with different "accounts" for different users. For example, my Mac is set up with 3 accounts: Mine (administrator), my wife (administrator), and guest user. In this fashion, I only see my email in Mail when I'm logged in to my account, and the same for my wife...she only sees hers.
Sometimes, these "account" settings get corrupted to the point where something no longer works, but creating a new account gets it working again.
Or...your problem may have something to do with TurboTax in this latest version. I've not yet installed TurboTax 2012 on my iMac, but have never had the problem you describe in any previous year (and I've used it for more than 10 years).
Do you get the same results if you try to save the file to, say, a USB flash drive?