the name of the checkboxes is not valid, form element names cannot contain spaces. The checkbox name:
confirm by[]
should be changed to:
confirm_by[]
to fix the error, in the Blank_12.php file, edit line 44:
if (get_magic_quotes_gpc()) $pval = stripslashes($pval);
to:
if (get_magic_quotes_gpc()) $pval = stripslashes((is_array($pval)?implode(", ",$pval):$pval));