OK, this one is hard, and I had to do this on some of my hosts also.
What I did was (before I had to rebuild my VC database) was this.
Disconnect the host from the cluster. Remove the host in VC (this will remove ALL VM's and associated templates) from the cluster. If you need your VM's or templates, migrate them first, but if your host is disconnecting this may prove awkward.
Then you login to the host, and the cluster should have abslutely no reference to that host at all. Once you are in the host, delete vimuser, and vpxa user. Then reboot the host, then login to the host as root first, ensure that you ONLY see VM's no left over resource pools, or anything, just VM's and templates (which are probably VM's). If it's empty even better, but make sure there is nothing from the previous cluster on this host.
Now add the host to the cluster while remaining as the root. At this point you have 2 VIC sessions one directly to the host and one directly to the VC. As the machine is added you will see messages on the host, and after its up and attaching to the cluster, it should calm down and give you no more problems.
I kept getting "resource added, logged in as root, root disconnected, every 10 seconds". This should not happen, and I finally had to start over with a new database to fix it. Previously this worked just rebooting the host, and removing the vpxa and vimusers, and letting the cluster re-add them.. but you will note that VC 2.5 does not readd these, and I am thinking that there is some left over stuff that isn't quite fixed yet with lingering previous hosts.
I hope this works for you, because I sat for 12 hours and tried everything, and never really did resolve the issue, but maybe you will be better off than me. The messages give you a clue, perhaps you can make better sense of them than I did.
