Two notices + problem with comments field can´t be turned off

Hi,
FYI: I have two notices in debug bar:

NOTICE: wp-content/plugins/post-indexer/includes/functions.php:398 - Undefined variable: post

NOTICE: wp-content/plugins/post-indexer/includes/functions.php:398 - Trying to get property of non-object

On this site I have problem with comment field - I cant turn off comments. I done this in certain page setup, I tried plugin Disable Comments and nothing help me.

If I delete [globalrecentposts number="7" title_link="yes" content_characters="200" show_avatars="no"] the comments are off.

Bigdrobek