Getting "Invalid Post Type" upon filtering from the Category dropdown

Hi

When Going to Dashboard -> Posts ->All Posts and then selecting the category filter drop down , I am getting a “Invalid Post format” error,

The URL giving the error is /wordpress/wp-admin/edit.php?s=&post_status=all&post_type=Array&_wpnonce=4203b19b7d&_wp_http_referer=%2Flangoor%2Fmistral%2Fwordpress%2Fwp-admin%2Fedit.php%3Fs%26post_status%3Dall%26post_type%3Dpost%26action%3D-1%26m%3D0%26cat%3D78%26seo_filter%26paged%3D1%26mode%3Dlist%26action2%3D-1&action=-1&m=0&cat=77&seo_filter=&paged=1&mode=list&action2=-1

When we change the post_type from Array to “post” , it works fine but that does not appear as default.

Screen Shot here http://imgur.com/EhsIAvW

Thanks.