Have you tried uninstalling DataAssist, deleting Dreamweaver's cache file and reinstalling DA again?
Have you tried deleting the complete Configuration folder that Dreamweaver's cache file sits in. A bit drastic as you have to reinstall all your extensions again but if it works...
Make sure you back it up first that way you can re-import your snippets etc. It also allows you to re-instate it in case it all goes pear shaped.