Hi Just purchased today and have the same issue, I have contacted my host about port 80 but not yet had a reply, I am a Heart Internet reseller and havn't had any issues in the past with running port 80 scripts.
UPDATE from Host
Please be aware that http loopbacks are not available on the shared servers, this is where a script calls [external links are visible to admins only] to call a file. I think the generator may be using http loopbacks in their scripting. I would recommend checking with its developers to confirm this. If it is indeed using http loopbacks, this script could not be run on the shared servers.
So is it not possible to run XML sitemap?