Shoutbox

You should be able to see them online again when they're, unless they have blocked you.

If they are sure they haven't blocked you, then there must be a problem with servers.

Also you should be able to send e-mails to them, nothing can ruin this action imho. In contact list right click on one of those contacts and select Send another>Email (email@com) [Menu items may not reflect the original English version]