Thread:Project:Support desk/Web Updater Error

MediaWiki - 1.15.1 (trying to upgrade to 1.18.1) PHP - 5.2.17 MySQL 5.0.92

I'm trying to complete an upgrade to 1.18.1 from 1.15.1. I don't have shell access to run the update script so I have to use the web updater to update the DB structure unfortunately. I get a weird error when trying to do this:

Fatal error: Class 'DatabaseInstaller' not found in D:\Hosting\*******\html\wiki-new\includes\installer\MysqlInstaller.php on line 15

Any help would be appreciate. I'm fairly certain I have upgraded all the extensions as well. Thanks.