having a 2-node Cluster (OES11SP2; iManager 2.7.7) wich runs fine but after
the last updates the Ability to manage the Cluster is gone :-(

After choose the "My cluster" Button it appares a window which explains: "
Failed to retrieve status information about cluster ... vie master ip
address ...."

Then I can choose a Cluster node by hand but this does not help, I get only
a yellow ? sign.

eDir is fine (time sync & partition sync)
no error seen in iManager debug file
no error seen in /var/log/messages
ldap is running
server certs are valid

What should I check next?

Any hints are welcome.