To cut a long story short the reason was corrupted system files and with the help of Microsoft Support (I can't praise them enough) who carried out a remote Windows repair installation, I'm finally up and running again with no loss of data.
I've now taken measures to significantly reduce the possibility of this happening again and if it does it won't break my flow the way it has this time.
Problem now is that I'm way behind with answering emails, writing posts and camera tests. I'll try and catch up in the next week or two but if you are waiting for a response from me you can short circuit the delay by calling me on +44 (0) 1456 415726 or making a contact request to ron.bury on Skype.
If I don't answer when you call, please leave a message and contact details so I can get back to you a.s.a.p