Yeah, that.
It looks like, either in the process of trying to fix it, you have removed some necessary files, or you were missing them to begin with.
I would start by re-uploading everything (keeping your inc/settings.inc.php) and if that doesn't work, a reinstall.
However, when it comes to a complete reinstall, at this point I would say that, unless you're in a big hurry, wait a day or two, as we'll be releasing an update this week and it would save you the trouble of upgrading.