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 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" at 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.  

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