Hi Mackavi,
I took a chance and deleted everything under Digital Workshop and then reinstalled Opus 9.75.
EDIT: I think I misread your instructions and just deleted the HKEY_CURRENT_USER entry, anyway it worked OK - relief!It now seems to work perfectly. This is a huge relief to me, I have now got an emergency folder on my laptop with the Opus exe file and key ready to repair my machine should I get this issue in a crisis situation. Fortunately this happened when I was at my desk rather than about to start a presentation.
I guess since you knew the solution, this (or something similar) must have happened before.
In the past I have tended to run my presentations directly from Opus (easy to make last minute changes), I think in future I will publish the presentation, as a back-up, and then if the program fails I can revert to the published veersion (a bit belt and braces).
For interest I see that I should have also gone into HKEY_LOCAL_MACHINE and treated this in the same way as HKEY_CURRENT_USER.
Interestingly Text Art is still working in Xara, I notice that Text Art is still in the Digital Workshop registry folder, I need to explore what this means.
Thank you again for your help, hugely indebted, BRILLIANT!
.
Martin