This may be an issue related the a problem with the cache file in Dreamweaver. You should try deleting this file to see if gets you past this error. Here is a link to a thread that lists where this file can be found, it is message 6 that has the paths.
Once you delete this file make sure to restart your machine before you attempt to use the tool again. Let us know if the issue persists.
showthread.php?t=1589