First of all.. seriously GREAT module.

The issue is if the drupal tables have a prefix (ie drupal_node) the module doesn't recognize that and it throws the error "table dragdrop_gallery doesn't exist". In my case I always use "drupal_" for my table prefix so the reason it "doesn't exist" is because it should be "drupal_dragdrop_gallery". The fix is very easy just in every SQL query in the .module file replace dragdrop_gallery with {dragdrop_gallery} and the db_query function will put in the prefix for you. I did it on my copy and it works great.