Error messages with Post Indexer

Post indexer seems to be indexing all the posts, but it is showing the following errors in 2 places on the page:

Warning: fopen(/home/mysite/public_html/wp-content/plugins/post-indexer/post-indexer.php): failed to open stream: No such file or directory in /home/mysite/public_html/wp-includes/functions.php on line 3879

Warning: fread() expects parameter 1 to be resource, boolean given in /home/mysite/public_html/wp-includes/functions.php on line 3882

Warning: fclose() expects parameter 1 to be resource, boolean given in /home/mysite/public_html/wp-includes/functions.php on line 3885

I haven't done anything with the posts except for indexing them, so I don't know if anything else is going to go wrong.

Thanks, Jill