>I normally just deploy the DLL file.

I have now realised that I have to be logged on as local Admin and not as domain Admin to register the dll. This is perhaps obvious with hindsight but I do not recall having ever seen a reference to this point in all the reading I have done on this subject. Or at least, being logged on as Local Admin has worked on my W7 client, so I am now a happy chappy!

Barry.