I've got a 16-node OES2 SP3 linux cluster

I've got 2 OES11 SP2 64-bit servers with the same iManager version and same plugins on them.

On the one server (not fully patched, so it doesn't have the recently released OES 11 patch), I can go to My Cluster just fine and it finds the Master Node and all is well.

On the OTHER (fully patched) OES11 SP2 server I get this error in iManager:

Failed to retrieve status information about cluster NCS1 via master IP address

Do you want to select a cluster node (preferably the master node) to manage the cluster?

Please note that the selection will be temporary. You need to select again whenever "My Clusters" page loads.

Please use this opportunity to fix the master IP address.
I browse to ANOTHER cluster node and all is well. OF course, I Have to do this every time I use THAT iManager server.

Now the question of course is:

If there truly was a problem with the Master IP stuff, why would one server work and one would not?

Seems to me to be an iManager plugin issue???