I 'upgraded' from 9.5, but I put that in quotes because it doesn't really do an upgrade- it installs a new copy with a different version number. How I did things is the issue, and it's really fairly simple in the end.
First thing I did was install the new version. Then when I opened the Opto submenu in Windows, I saw that I had two of everything, but with different numbers (9.5 and 9.6). So, I went back and uninstalled 9.5 to get rid of the duplicate programs- that was where it all went south.. the uninstall removed a file that's needed. So, I uninstalled ALL the versions, and reinstalled the new one, and it's all good now.
Basically it's this- to 'upgrade', remove the old version FIRST, then install the new version.