Sitemap Generator Forum

I have multiple sites on the same shared server at same IP, most are generating XML sitemaps flawlessly but a few give back this error:

An error occured
There was an error while retrieving the URL specified: [ External links are visible to forum administrators only ]
HTTP Code:

HTTP headers:
x_csize: 0

HTTP output:

Probably there is a configuration problem - it looks like your server doesn't allow local network connections via port 80 (http) or 443 (https) - as a result sitemap generator is not able to crawl the site. This is usually related to firewall installed at the host - could you please contact your hosting support regarding this?