What is the version of DataAssist that you have installed?
There are two things you should try. The first is to delete the cache file that is in the configuration folder. I'm including a link to a troubleshooting page with instructions on deleting this file, it will be the MacFileCache file for you.
The other thing to try is to make sure you have all of your panels closed before you run the wizard. A while back I saw an issue like this that would happen when the files panel and others were open, closing them before running the wizard would help with this. Please post back and let us know your results.