Since you're able to cluster QlikView Servers with a special license QVS will automatically broadcast on the net it's on to see if there are servers to cluster with running the same license. This requires the license to be a cluster license with a value for Cluster_Nodes set to more than one. Otherwise the QlikView Server services will go down every 10 minutes with the Cluster Joined Denied error.
Make sure that there is no other machine running the QlikView Server Service with the same license key and the problem should go away.
If you are unable to locate the machine please get in touch with Support who will help you out.
Well, there's no gain in turning it off since it's against the license agreement to use a license (non cluster license that is) on more than one QVS instance. It actually serves a purpose disrupting the service every 10 minutes in those cases. So no, all licenses will broadcast and try to cluster with identical license numbers.