6
Some severs do not allow you to chmod to that low of level.(weird though you are the admin, right?)
Even though through FTP says it is 644 or 444, you still get the warning.
So when all else fails, try to bypass with PHP.
Create a file named chmod.php
Add this:
<?php
chmod('mainfile.php', 0444);
?>
Save, upload to your XOOPS directory and open.
http://www.yoursite.com/chmod.php
Once you open up the file, DELETE it.
No More errors.
PEACE