unlink problem with Advanced Guestbook 2.3.1

I managed to get it setup and running, however, when a message is posted, it gives an error:

Warning: unlink(index.html) [function.unlink]: Permission denied in /home/virtual/site2/fst/var/www/html/gbooktest/lib/add.class.php on line 80

The Directories "public" and "lib" are setup for Write Permission 777 as the manual said.

put a '@' before the unlink function

@unlink(....