DB QUERY ERROR (one_row_query()): Out of resources when opening file './backstroms_2016/admin_modules.MYD' (Errcode: 24 - Too many open files)

SELECT IF(CHAR_LENGTH(seo_title), seo_title, (SELECT name FROM admin_modules WHERE moduleid = 1)) AS seo_title, seo_keywords, seo_description FROM admin_modules_seo WHERE groupid = 4 AND moduleid = 1