PHP error with bulk edit

Warning: Illegal offset type in isset or empty in /Sites/www/wp-includes/cache.php on line 618

Warning: array_key_exists() [function.array-key-exists]: The first argument should be either a string or an integer in /Sites/www/wp-includes/cache.php on line 618

Warning: Cannot modify header information - headers already sent by (output started at /Sites/www/wp-includes/cache.php:618) in /Sites/www/wp-includes/pluggable.php on line 876

When I bulk edit just one post, it works, bulk editing more than one generates the error.

WP Version: 3.5.1
Plugin version: 1.2

https://www.ads-software.com/extend/plugins/post-type-switcher/