Save as Template caused issues?

I installed Scrivener on a new laptop running Windows 10 a few weeks ago. Everything was fine, although I had not yet tried anything fancy like setting up my backup to Dropbox.

Today I clicked on a completed manuscript folder and hit FILE>Save as Template, thinking today was the day I would start a new manuscript (apparently not). After that everything seems to have gone haywire. It started freezing, the icons when I go back up are black boxes (and it won’t show me any options outside of Documents-- e.g., can’t see “This PC”), and it takes ages to reopen the original project once I’ve closed it.

I uninstalled and reinstalled. That didn’t help. What has happened and how can I fix this? I greatly appreciate any advice.