If you’re using Openinviter, you probably got this error while trying to use the Twitter service:
'Unable to get contacts'
Same thing will happen using the online demo.
This is due to a recent Twitter update forcing SSL on mobile version (The Openinviter plugin is not using the official API methods but a clever interaction with the mobile version of Twitter).
To fix that issue, just open the /OpenInviter/plugins/twitter.plg.php file and change all the http references to https.
Btw, this will also fix the send invitations problem (if you ever succeeded to get contacts).
It should work flawlessly