I had the same problem.
Use this it only deleted the dupes. To be on the safe side you should run it as a select first. AND back up your DB
DELETE bad_rows.*
from wp_posts as bad_rows
inner join (
select post_title, MIN(id) as min_id
from wp_posts
group by post_title
having count(*) > 1
) as good_rows on good_rows.post_title = bad_rows.post_title
and good_rows.min_id <> bad_rows.id
