Google Talk and AOL Instant Messenger (AIM) interoperability problems. Not yet time to ditch AIM in favour of Google Talk.
If you use you have your own XMPP network enabled on your Google Apps Domain, you will not be able to turn-on Google Plus support.
Google Apps XMPP network currently have a bug, and it is hard to get their attention and fix this issue unless you are “somebody”. No doubt it’s their bug.
Chat with YM/MSN/ICQ/AIM messenger buddies inside Google+ / Gmail. How? Follow these simple steps.