Related posts picker and headers already sent by…

Hi all.
Just installed this great plugin, and I can see related posts on my pages. But when I try to edit any old post I see this

Warning: implode() [function.implode]: Invalid arguments passed in /home/krekadra/public_html/wp-content/plugins/related-post-picker/related-post-picker.php on line 147

Warning: implode() [function.implode]: Invalid arguments passed in /home/krekadra/public_html/wp-content/plugins/related-post-picker/related-post-picker.php on line 147

Warning: Cannot modify header information - headers already sent by (output started at /home/krekadra/public_html/wp-content/plugins/related-post-picker/related-post-picker.php:1) in /home/krekadra/public_html/wp-includes/pluggable.php on line 897

Or this

Warning: Cannot modify header information - headers already sent by (output started at /home/krekadra/public_html/wp-content/plugins/related-post-picker/related-post-picker.php:1) in /home/krekadra/public_html/wp-includes/pluggable.php on line 897

After button “Update” pressed.
This text I see in Simple Tags plugin “click tags” area:

Warning: Cannot modify header information - headers already sent by (output started at /home/krekadra/public_html/wp-content/plugins/related-post-picker/related-post-picker.php:1) in /home/krekadra/public_html/wp-content/plugins/simple-tags/inc/class.admin.clickterms.php on line 73

I have disabled Simple tags, but it did not help.
Also if I picked 1 or more related posts in edit mode, then it is only “Related posts” header visible on page. No related links.

Any ideas?