File should not contain more than 1500 rows. ERROR Message

File should not contain more than 1500 rows. ERROR Message

I'm trying to import a CSV file of leads.  The CVS contains 1449 rows (including header).
I select the file and click the Next button.

The page thinks and then the following Popup appears:

File should not contain more than 1500 rows.


I am using the Free Version of CRM, however the limit has not been reached. Not sure why I can't import?