I finally had a chance to look at this issue on my local OS X 10.8 machine. With the update to 10.8 Apple changed how Apache is setup, and line 11 in library.php of Data Assist sets the directory name using PHP_SELF. Well, if you don't have everything setup in your user.conf file located in /etc/apache2/users then this file just hangs. I seem to have added the config info necessary to have everything running correctly. Why nothing else broke I have no idea.
FYI-You have to add a <VirtualHost *.80> entry for localhost