What Has Changed?
Upgraded from 3.0.2 to 3.0.1 or something like that, I was clearly on 3.x
What Have I Attempted?
What would you do next?
I had some problems upgrading to 3.0.3 on a multi-site installation. I had used the automatic upgrade and it failed, but luckily, downloading and extracting the new files from WP.org and uploading them directly fixed it. I would try that first. If that doesn’t work, try re-uploading your backup files. You did make a backup, right?