We got following problem some days ago:
One of our ESX (version 3.5) hosts, after crash, was not connecting to Virtual Center (version 2.5).
Solution:
- Restart management service on ESX host
service mgmt-vmware stop
service mgmt-vmware start
- Restart Virtual Center service on Virtual Center server (stop/start on service VMware Virtual Center in Services)
One more stuff - if you have a lot of memory on your hosts (16 GB or more) I would recommend you to increment amount of console memory on your host to 800 MB. You can do this in "Configuration" tab for host in your Virtual Center console.