Thread:Project:Support desk/Class 'ResourceLoaderWikiModule' not found in SyntaxHighlight GeSHi.local.php/reply

Apparently, you're using a trunk SyntaxHighlight_GeSHi with a release version of MediaWiki. Such mix is not guaranteed to work, so pick up a proper version of the extension from Special:ExtensionDistributor/SyntaxHighlight_GeSHi.