Hi Ray
the problem resolved it's self in that when Dreamweaver and the webassist were not responding I left them and after two hours the PC was still locked out. So I went to bed and when I got up it had all cleared its'self and worked.
it seems as if the extension was using the option to install despite the fact that before strting Dreamweaver I downloaded and saved the extension and then did a manual install using extension manager cc.
Any problem solved
thanks
Ian