I just installed a brand new ESX 4.0 Host and i did some configuration changes that required a reboot. As usually a put the host in maintenance mode and gave the system a reboot within the virtual infrastructure client. The nice thing with the new version is that the client will automatically reconnect to the host after the reboot. And it happens as it should, but in the summary tab of the ESX host it says Reboot Required! Why? Oka if you say so, so gave the host another reboot.
But he was persisted. So after one shot without manual or Google I thought it was time to find out what is this little thing that isbothering me. I found out it was a known error it says eary version of the software are not used to reconnect and that is why it says reboot required but he this is new software? The solution is as simple as Microsoft solutions close the client and make a new session with the host or vCenter. So do a client connection rebuild to get ridge of the message or don’t let the message bother you.
This issue is registered under VMware KB1012206.