Have you tried disabling the plugin from vCenter (Plugins->Manage Plugins) and than re-enabling it after the second installation, when you will choose "integrate with vcenter"?
not yet, will give it a try next week. I thought it might be described in some manual or other paper, but i could not find it anywhere.
Could you please change old syslog server port from 514 to any free port
hope it will help you .