Stai selezionando b.blog_id e raggruppamento per e.blog_id . Questo è il problema.
SELECT MAX(e.entry_id) as max, MAX(e.entry_date) as maxdate,b.blog_id, b.blog_name, b.blog_seo_name
FROM blog_entries e LEFT JOIN
blog_blogs b ON ( b.blog_id=e.blog_id )
WHERE e.entry_status='published' AND e.entry_banish=0 AND e.entry_featured=0
AND b.blog_view_level='public' AND b.blog_disabled=0
GROUP BY b.blog_id, b.blog_name, b.blog_seo_name
ORDER BY maxdate DESC LIMIT 0,50
