I found the solution. The problem is that in the Joomla table update_sites, there is an unneccessary space before the CMC Updates URL like this:
" https//
http://compojoom.com/index.php?option=com_ars&view=update&task=stream&format=xml&id=13&dummy=extension.xml"
^
|_ see the space? (By the way, I had to remove the colon from the URL, otherwise Kunena kept rendering it as a link.)
Remove the space and the Joomla and Extensions update checks work in the control panel.
I found it on the previous version, but I thought you'd have found it so I didn't report back. I just upgraded to 1.4 and the space is back again, so I thought I ought to let you know.
Hopefully, this will help anyone else having the same problem.
Hey Jason,
the problem is that the hotspots update url uses encrypted connection (https) and your server is not configured properly to handle this (is this a local xampp or wamp installation???).
You can login with phpmyadmin and navigate to the #__update_sites table and disable the cmc update url.
Regards,
Daniel