I reported this same problem to GS Australia last week. It is happening with both Mac and PC for us, so it is not OS specific. Some machines seem to work OK but most show the libraries as 'Unavailable' instead of 'offline'.
I think it may have something to do with using the IP address of the BIM Server instead of the full networked computer name, but I am yet to confirm this 100%. If this is the case, I am sure it is not the intended outcome. ( in other words, a bug).