Delete all stores in one shot

Are you using the 1.x, or 2.x version?

Run this query in phpMyadmin to delete all the wpsl_stores posts. Do replace wp42_ with the name of your own db.

DELETE a,b,c FROM wp42_posts a
LEFT JOIN wp42_term_relationships b ON (a.ID=b.object_id)
LEFT JOIN wp42_postmeta c ON (a.ID=c.post_id)
WHERE a.post_type='wpsl_stores'