I have not been able to recreate this issue. I am running Clearspace 1.8 with PostgreSQL as the database and Openfire 3.4.1. Both are using the same LDAP server.
I can successfully setup the Real-Time connection and presence in Clearspace and if I stop Clearspace without closing the connection to Openfire, when I restart the appserver, Clearspace comes back up and reconnects to Openfire successfully.
Am I missing any steps in my attempts to recreate?
Can you clear out all your logs from both Openfire and Clearspace, then recreate the issue and send over the logs from both to firstname.lastname@example.org so I can take a look?