looks like the same problem in other thread here. So the same questions: have you tried to kill problematic session in Admin Console and login again? And can you tell what are your shared groups configuration?
Glad to hear that groups are working fine for you. Anyway, if you want to include someone to your roster remember to use the bare JID (eg johndoe@server.com) and not just the username (eg johndoe). Once you added a new contact to your roster the other user will receive a presence subscription which he may or may not accept. If the user accepts the presence subscription then you will be able to see him when he is online/offline.