Cluster resource in UNASSIGNED state

We have a 2-Node Cluster on OES2 Netware SP6 and Post Patches.
Sometimes we get a status that the CMON shows both nodes Online but in
C1 all Nodes are greyed out. At the console cluster status command shows
one resource (GW7) as UNASSIGNED. It is not possible to set the resource
to OFFLINE or to migrate. I can send the commands but the reply is only
the status of the rsource - nothing happens. I have to reboot the
servers in this case.