I successfully turned a theme into multisite. Everything was running great. I wanted to change the theme of the main site (I only have one site so far). The new theme is based on twentyeleven. I changed all the references to twentyeleven to my-new-theme. I ftp'd my-new-theme to the server, activated it, and the site and dashboard crashed.
I then went into phpadmin ran this:
WHERE option_name = 'template'
OR option_name = 'stylesheet'
OR option_name = 'current_theme';
and changed it back to Twenty Eleven, twentyeleven, twentyeleven.
Still broken. I can't access the dashboard or the front end.