Thread:Project:Support desk/Upgrading Issues 1.12 -- 1.18/reply

Did you remember to remove the old files? In general, I don't like overwriting; I typically would make a new folder for the new MediaWiki installation, and move the LocalSettings.php file there. Then, I'd rename that new folder to the desired name after renaming the old folder to an old name. After that I'd run the installer.