you mention that you have deleted the configuration folder only, then reinstalled the extension.
My suggestion was to delete a single file from the configuration folder _after_ installing the extension.
if you still have a problem after deleting the Dreamweaver cache file, please provide some additional details on your set up:
What Is you OS?
What version of Dreamweaver?
Have you defined a site in Dreamweaver?
Have you created a new htm or PHP file and saved it to that site?
is this new file open when you launch Menu Writer?
can you provide details on how the site is defined, such as local folder?