make sure you have completed the following steps before running the site assist professional wizard:
1) Create a Site with in Dreamweaver
2) Create a new page and save it to your Dreamweaver site.
3) Have that page open in Dreamweaver.
When deleting the Dreamweaver cache file, make sure that Dreamweaver is closed.
In some cases, you may need to restart the computer and delete the cache a second time.