Thread:Project:Support desk/'Do not run update.php on this wiki' error

After installing the BibManager extension, I tried to run update.php as per the admin manual and got the following error:

This thread says that this problem can occur with $wgMiserMode enabled on MediaWiki 1.18.0, but I've never used that in any way. I can't find any other references to the error. It persisted even after uninstalling BibManager.

I'm new to Mediawiki and not very knowledgable about things yet, any help would be very much appreciated.

Mediawiki: 1.18.0

PHP: 5.3.x+fastCGI

Database: MySQL 5.0