Did you completely uninstall and reinstall DataAssist when you last upgraded. Dreamweaver has a nasty habbit of not adding new files when you don't uninstall the old version. That sounds like it could be the issue.
Or I have attached a copy of the file to this thread. You can add it to your user configuration folder in the location:
/%appdata%/Adobe/Dreamweaver CS5/en_us/Configuration/Shared/WebAssist/ApplicationBuilder/Helpers