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 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
For more info on Fuse for OSX visit link: http://osxfuse.github.com/
*You must check the box "MacFUSE Compatibility Layer" at the installation screen."
macfuse_ss

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
For more info on NTFS 3G Driver visit link: http://sourceforge.net/projects/catacombae/
*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 Windows XP environment, download and install the 
KB955704 update.

The Enterprise and DL3 support multiple partitions and formats allowing you to create numerous partitions with different formats depending on your needs.