The problem is nothing to do with your wp-folders. It’s a problem with your Apache configuration.
If you have ftp access, edit your .htaccess file to turn Mod Sec off:
<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>
If you don’t, contact your webhost and ask them to do it for the folder containing your blog.
