My sql error on activating Marketpress

I've got this error on store page.

Situation:
I have no products in the shop

error message:
WordPress database error: [Not unique table/alias: 'wp_postmeta']
SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) join wp_postmeta on wp_postmeta.post_id=wp_posts.ID WHERE 1=1 AND wp_posts.post_type = 'product' AND (wp_posts.post_status = 'publish') AND ( (wp_postmeta.meta_key = 'mp_sales_count' AND CAST(wp_postmeta.meta_value AS CHAR) > '0') ) GROUP BY wp_posts.ID ORDER BY wp_postmeta.meta_value DESC LIMIT 0, 5