Fatal G2 error

Here's the error from G2: Error (ERROR_MISSING_OBJECT) : Parent 7 path londonexpo

in modules/core/classes/helpers/GalleryFileSystemEntityHelper_simple.class at line 98 (GalleryCoreApi::error)
in modules/core/classes/GalleryCoreApi.class at line 1952 (GalleryFileSystemEntityHelper_simple::fetchChildIdByPathComponent)
in modules/core/classes/helpers/GalleryFileSystemEntityHelper_simple.class at line 53 (GalleryCoreApi::fetchChildIdByPathComponent)
in modules/core/classes/GalleryCoreApi.class at line 1901 (GalleryFileSystemEntityHelper_simple::fetchItemIdByPath)
in modules/rewrite/classes/RewriteSimpleHelper.class at line 45 (GalleryCoreApi::fetchItemIdByPath)
in modules/rewrite/classes/RewriteUrlGenerator.class at line 103 (RewriteSimpleHelper::loadItemIdFromPath)
in modules/rewrite/classes/parsers/modrewrite/ModRewriteUrlGenerator.class at line 56 (RewriteUrlGenerator::_onLoad)
in init.inc at line 186 (ModRewriteUrlGenerator::initNavigation)
in modules/core/classes/GalleryEmbed.class at line 129
in /home/mlnert/manylemons.co.uk/wp-content/plugins/wpg2/wpg2embed.inc at line 43 (GalleryEmbed::init)
in /home/mlnert/manylemons.co.uk/wp-content/plugins/wpg2/wpg2embed.inc at line 95
in /home/mlnert/manylemons.co.uk/wp-content/plugins/wpg2/wpg2template.inc at line 46
in /home/mlnert/manylemons.co.uk/wp-includes/class-wp-hook.php at line 287
in /home/mlnert/manylemons.co.uk/wp-includes/class-wp-hook.php at line 311 (WP_Hook::apply_filters)
in /home/mlnert/manylemons.co.uk/wp-includes/plugin.php at line 478 (WP_Hook::do_action)
in /home/mlnert/manylemons.co.uk/wp-includes/template-loader.php at line 13
in /home/mlnert/manylemons.co.uk/wp-blog-header.php at line 19
in /home/mlnert/manylemons.co.uk/index.php at line 17