Thanks Emmanuel,

I can SAVE and I can SAVE-AS.

When I choose CLOSE or EXIT, nothing happens, the screen stays exactly the same.

After forcing the closure with the Task Manager when I re-open SH3DI I get a 'recovered' file which is not the last state I left the file in. I then manually OPEN the last file and it is as I would expect. At the moment I'm saving the file twice under two different names because I have done a lot of work.

Nothing else behaves like this on my PC and I have never seen this happen before.

Does the paid for Windows Store version completely overwrite the Source Forge version ?

Seth.