Sounds like you need to change the permissions of the file on your server. You can use your web hosting control panel or an FTP program to browse to the file that is listed (ieL ../_post_comment.php) and change the permissions on that file to 766.
(I think thats the correct numerical format) Basically, you need to give read and write permissions to everyone.

The 404 error sounds like you have an htaccess file set up to use custom error pages and you don't have a copy of that file, 404.shtml, on your server.

Here's what was in my .htaccess file in my /blogs folder
# Apache configuration for the blog folder

# this will select the default blog template to be displayed
# if the URL is just .../blogs/
<IfModule mod_dir.c>
DirectoryIndex index.php index.html
</IfModule>

# this will make register globals off in b2's directory
# just put a '#' sign before these three lines if you don't want that
<IfModule mod_php4.c>
php_flag register_globals off
</IfModule>

# If you're using Apache 2, you may wish to try this for clean URLs:
# AcceptPathInfo On

# Fix for comments
RewriteEngine On
RewriteCond %{HTTP_REFERER} !^http://yourdomain.net/.*$ [NC]
RewriteCond %{REQUEST_URI} ^.*comment_post\.php$
RewriteRule .* - [F]

RewriteCond %{HTTP_REFERER} \.us [NC,OR]
RewriteCond %{HTTP_REFERER} \.info [NC,OR]
RewriteCond %{HTTP_REFERER} \.biz [NC,OR]
RewriteCond %{HTTP_REFERER} \.ru [NC,OR]

Here's my .htaccess from my root

<Files 403.shtml>
order allow,deny
allow from all
</Files>

deny from 209.97.207.86
deny from 66.119.41.71
deny from t-ipconnect.de
deny from migtel.ru
deny from .info
deny from .us
deny from .biz
deny from .mx
deny from .il

boarder_in_co wrote:

# Fix for comments
RewriteEngine On
RewriteCond %{HTTP_REFERER} !^http://yourdomain.net/.*$ [NC]
RewriteCond %{REQUEST_URI} ^.*comment_post\.php$
RewriteRule .* - [F]

This entry could be causing the problem. Did you try to access the comments page from www.yourdomain by any chance? The htaccess directive will block any access to comments from anything other than http://yourdomain.net

Yeah.

Replace "http://yourdomain.net/" with your actual domain name.