Actually, right now, as we speak, its between many many users. Believe me.

But if you want to troubleshoot it, both of you delete each other as contact in your BBMessenger list.
Do a powered on battery pull reboot. Confirm neither of you is in the others Contacts on BBM... now one of you add the other back via PIN.

And if it doesn't work for a couple hours, don't be surprised.

For example, right now I can BBM with a friend in CA, but another in OR and NJ, we cannot.