After upgrading to Filemaker 12, MYOB is not recognising tab delimited (.TAB) files during the import process. This is only occurring in Mac OS/X. The exported file appears greyed out via the import steps in MYOB so cannot be selected.
Changing the extension of the .tab file to a .txt file does resolve the issue. We will continue to monitor the FileMaker Pro 12 update releases to test if the issue is addressed by FileMaker.