I have the same problem on my mac. But on another mac (where display driver software hadn't previously been installed) it worked fine after the installation..
I have tried to reinstall. Nothing seems to help..
Made a thread about it, but no one seems to be able help.
Link to the thread:
http://www.displaylink.org/forum/showthread.php?p=69997
Another thread with the seemingly same problem:
http://www.displaylink.org/forum/showthread.php?t=61741