Código PHP:
SELECT A.topic_title,
B.poster_id,
B.post_id,
B.post_time,
C.user_id,
C.username
FROM phpbb_topics A, phpbb_posts B, phpbb_users C
WHERE C.user_id = B.poster_id
AND A.topic_id = B.topic_id
ORDER BY B.post_time
DESC LIMIT 10
mmmm que soluciones veis? gracias!