When a particular ESX host is showing a disconnected status, and attempts at reconnecting are failing, a simple way to regain full control of the ESX host is to restart the ESX host and server management agents.
This process allows the administrator to place the ESX server back into the virtualcentre for further investigation and control of any running virtual machines.
This is performed by connecting to the ESX console eithier physically or by using SSH.
service mgmt-vmware restart
service vmware-vpxa restart