Hello,
You should not use D2XX drivers but VCP (virtual com port drivers). They could be found :
http://www.ftdichip.com/Drivers/VCP.htmThis is for the ENTTEC DMX USB PRO.
Here are the steps to ensure that you FTDI driver is well installed.  
1) plug the ENTTEC DMX USB Pro on an USB port (one with enought power to drive this device)
2) verify that the driver loads after plugging it in using Applications|Utilities|Terminal
mac-pro-de-david-geldreich:~ dgeld$ kextstat  | grep com.FTDI
 114    0 0xcd0e9000 0x7000     0x6000     com.FTDI.driver.FTDIUSBSerialDriver (2.2.14) <99 38 12>
3) verify that the device is seen :
mac-pro-de-david-geldreich:~ dgeld$ system_profiler SPUSBDataType
...
       DMX USB PRO:
         Product ID: 0x6001
         Vendor ID: 0x0403  (Future Technology Devices International Limited)
         Version: 6.00
         Serial Number: ENQEJNRZ
         Speed: Up to 12 Mb/sec
         Manufacturer: ENTTEC
         Location ID: 0x1d100000
         Current Available (mA): 500
         Current Required (mA): 300
4) verify that the driver created a /dev entry :
mac-pro-de-david-geldreich:~ dgeld$ ls -al /dev/tty.usbserial*
crw-rw-rw-  1 root  wheel   10,   6 21 jan 15:22 /dev/tty.usbserial-ENQEJNRZ
5) open Modul8 | Preferences | DMX
select ENTTEC, the device listed above, receive mode
go to Modu8 | Info | DMX
you should see the serial/firmware version of your decice
Regards