If you upgrade your vcenter then get errors when you esx servers are trying to update the virtualcenter agent.
Follow the directions in this post
http://communities.vmware.com/message/497546
To save you some time here is the directions that fixed the issue for me:
You could manually try to install the agent as follows:
– Copy the vpx-upgrade-esx-6-linux-32042 from the upgrade folder in the VC folder to /tmp on the ESX server
– run the command sh vpx-upgrade-esx-6-linux-32042
(By default the script is located in C:\program files\vmware\vmware virtualcenter\upgrade )
Next restart management services:
service mgmt-vmware restart
After completing the above steps, try to reconnect to the esx
Enjoy
jb