It does sound as if locale might be the issue (DMY vs MDY).
Just to be clear, please confirm the following:
a) The source is a spreadsheet with a date formatted in Australian format.
b) The target is a SQL Server 2012 datetime column
c) The import is running on the 2012 instance, which has a US locale.
If that is the case, as a test you could try opening up Excel and applying a custom date format to the dates in the spreadsheet (something like m/d/yyyy). Does that import?
If you haven't even tried to resolve your issue, please don't expect the hard-working volunteers here to waste their time providing links to answers which you could easily have found yourself.