When Data Assist crashes like this it is normally a result of a Dreamweaver Memory leak.
Restart the system, then Delete the Dreamweaver Cache file from the users configuration folder:
In the WebAssist -> Preferences, go to the preview section and disable the preview, you will still be see the preview if needed by clicking the preview placeholder.
before starting the Data Assist wizard, close the Files and Server Behaviors panels.
also, make sure that you have the latest Data Bridge version, 1.1.8, installed, it won't prevent the memory leak from causing a crash, but it does include a feature to remember your settings when it does crash so you can start back up without having to reconfigure everything.