Unfortunately, the plugin does not check whether
$_POST['pt_noncename'] is set before trying to use it in the
metabox_save( $post_id, $post ) function. This causes php errors/warnings.
I added the following at the beginning of that function (around line 112) to correct the issue:
if ( !isset($_POST['pt_noncename']) ) return $post->ID;
Hopefully, later releases will incorporate this or similar code to prevent errors or warnings caused by referencing variables that don't actually exist.