Thread:Project:Current issues/Site broken after upgrade with Call to undefined method MediaWiki::run()

Two days ago I upgraded from MW 1.16.2 to 1.18.2. At the same time I pruned and upgraded a few extensions. The last thing I did was leave a discussion page listing the upgrades.

Today when I returned I got this:

Fatal error: Call to undefined method MediaWiki::run in /home/nakedwiki/nakedwiki/index.php on line 57

Does anyone have any idea what might have happened and what I can do about it?

thanks!