I got the following fatal error after upgrading to 2.61. The blog seems to display okay, but I can't get into the admin/dashboard at all.
It may be because I didn't understand the instruction to delete all wp files. I did delete all files that begin with wp in the wordpress root directory. Is that enough?
Fatal error: Call to undefined function: add_thickbox() in /home/content/n/o/t/notjustjokes/html/wordpress/wp-admin/page.php on line 82
Prior to that I had an an error in wp-settings, and the blog wouldn't load, so I reinstalled the old file, which got the blog to load but created the error above.
The error in wp-settings (new file) was
Fatal error: Call to undefined function: force_ssl_admin() in /home/content/n/o/t/notjustjokes/html/wordpress/wp-settings.php on line 394