The TurboTax for Mac program is currently not allowing some customers to save their tax files.
Try the Save As option by holding down the Option key when selecting the File menu in TurboTax.
If that doesn't work, follow these instructions to uninstall and reinstall TurboTax. Your tax file will not be removed during this process aslong as it's saved in your Documents.
After you've reinstalled the program, eject your CD (if you're using one), update the program, and try again.