I’m suffering from the same problem: no more admin functions available while loging as admin works fine. I even lost some users in the Users list (only 4 out of 10 are displayed), alhtough “missing” users can also log w/o error.
I’m not that versed into command line tweaks, so can you please describe your solution a bit further? What do you mean by “I changed the desired setting in config.php”: which setting do you talk about? which new value did you set it up?
Correcting your database: did you use such a tool as phpmyadmin and did you throw some command line to perform the update?
Thanks in advance for any help!