Cannot start cluster services after fresh installation, cman fails with "fence_tool: cannot leave due to active systems"

Issue

• Starting the cman service fails with following error message:

   Leaving fence domain... found dlm lockspace /sys/kernel/dlm/rgmanager
fence_tool: cannot leave due to active systems
                                                           [FAILED]

• The following errors appear on a newly created cluster on RHEL6 servers with the latest HA packages. As a result, I am unable to start any services on any nodes:

# service cman restart
Stopping cluster:
   Leaving fence domain... found dlm lockspace /sys/kernel/dlm/rgmanager
fence_tool: cannot leave due to active systems
                                                           [FAILED]

# clustat
Timed out waiting for a response from Resource Group Manager
Cluster Status for wargames @ Thu Jul 26 14:02:41 2012
Member Status: Quorate

 Member Name                             ID   Status
 ------ ----                             ---- ------
 node1                      1 Online, rgmanager
 node2                      2 Online, Local, rgmanager
 node2                      3 Online, rgmanager

Service Name           Owner (Last)        State         
------- ----           ----- ------        -----         
service1                 (node1)           failed       
service2                 (node2)           failed        

• The cluster appears to hang at cluster stop

• A GFS2 filesystem will not mount on one of the cluster nodes, and restarting cman shows the error shown above