Looks like something got modified incorrectly. If there's a backup/previous revision of this file available, I'd suggest reverting to that instead.
Otherwise, you could try removing the duplicate blocks of code (starting with the line in red, minus the '}' closing brace); you should end up with something like:
function art_menu_items()
{
global $artThemeSettings;
if (true === $artThemeSettings['menu.showHome'] && 'page' != get_option('show_on_front'))
echo '<li><a' . (is_home() ? ' class="active"' : '') . ' href="' . get_option('home') . '">'.$artThemeSettings['menu.topItemBegin']
. $artThemeSettings['menu.homeCaption'] . $artThemeSettings['menu.topItemEnd'] . '</a></li>';
add_action('get_pages', 'art_header_page_list_filter');
add_action('wp_list_pages', 'art_list_pages_filter');
wp_list_pages('title_li=&sort_column=menu_order');
remove_action('wp_list_pages', 'art_list_pages_filter');
remove_action('get_pages', 'art_header_page_list_filter');
}
add_filter('comments_template', 'legacy_comments');
function legacy_comments($file) {
if(!function_exists('wp_list_comments')) : // WP 2.7-only check
$file = TEMPLATEPATH.'/legacy.comments.php';
endif;
return $file;
}
instead. There may be more invalid code after the line you stopped on, however.