I just tested it and you are right, it’s a hash issue; I will fix it as soon as I can.

If you are not afraid of doing a quick fix this is what you have to do. Replace the following code in the store.php file ( image-store/_inc/store.php ) line 893

}elseif( $gal->post_password === $pass ){
setcookie( 'ims_galid_' . COOKIEHASH, $gal->ID, 0, COOKIEPATH, COOKIE_DOMAIN );
setcookie( 'wp-postpass_' . COOKIEHASH, $gal->post_password, 0, COOKIEPATH, COOKIE_DOMAIN );
update_post_meta( $gal->post_id, '_ims_visits', get_post_meta( $gal->ID, '_ims_visits', true ) +1 );
wp_redirect( get_permalink( $gal->ID ) );
die( );
}

with

	}elseif( $gal->post_password === stripslashes( $pass ) ){
global $wp_hasher;
if ( empty( $wp_hasher ) ) {
require_once( ABSPATH . 'wp-includes/class-phpass.php');
$wp_hasher = new PasswordHash(8, true);
}
setcookie( 'ims_galid_' . COOKIEHASH, $gal->ID, 0, COOKIEPATH, COOKIE_DOMAIN );
setcookie( 'wp-postpass_' . COOKIEHASH,  $wp_hasher->HashPassword( stripslashes($gal->post_password) ), 0, COOKIEPATH, COOKIE_DOMAIN );
update_post_meta( $gal->post_id, '_ims_visits', get_post_meta( $gal->ID, '_ims_visits', true ) +1 );
wp_redirect( get_permalink( $gal->ID ) );
die( );
}