This is due to the current Mac OS's lack of write ability for NTFS formatted drives. Both the Enterprise and DL3 come pre-formatted with a widely-used Windows NTFS filesystem.  To use exclusively in a Mac environment simply format the drive on your Mac using the HFS+ filesystem.  

If you plan to use the Enterprise or DL3 between a Windows and Mac environment you have two options:

  1. Install Fuse for OSX
    Download link: https://github.com/downloads/osxfuse/osxfuse/OSXFUSE-2.4.2.dmg

    *****You must check the box "MacFUSE Compatibility Layer" on the installation screen.

    Install NTFS 3G Driver
    Download link:  http://downloads.sourceforge.net/project/catacombae/NTFS-3G%20for%20Mac%20OS%20X/2010.10.2/ntfs-3g-2010.10.2-macosx.dmg

    *****At the caching selection option, pick no caching best results.

  2. Reformat the drive in the exFAT format.  

    *****Some older operating systems may not be able to use the new exFAT filesystem.  

    Note: To use exFAT in the Windows XP environment, download and install the Microsoft Windows     KB955704     update.