ESX Server: Timed out

Putting this up as I couldn't find it via Google or the VMWare forums when I encountered this problem:

I have ESX Server 3 and Virtual Centre 2, and powered down a virtual machine that ran one of DNS servers. I have DNS running on both physical and virtual servers. I then found I was unable to start that virtual machine or any other virtual machine getting a "Timed out waiting for the server response" error in the Virtual Infrastructure Client. This is despite the fact that other non-virtual DNS servers were defined on the ESX and Virtual Centre servers. Name resolution on the Virtual Centre Server seemed ok, I flushed the DNS and was then able to check name resolution ok. I also tried unsuccessfully changing the default DNS server on the Virtual Centre server to a physical DNS server. I found closing Virtual Infrastructure client I was then unable to reopen the client and logon to the Virtual Centre server.

Not being able to start VMs was very disconcerting. To fix this I opened Virtual Infrastructure Client and logged directly to the ESX server hosting the virtual machine I powered down rather than the Virtual Centre server. I then sucessfully restarted the virtual machine running the DNS server. After this server was restarted, I then restarted the Virtual Centre server, then reopened the Virtual Infrastructure client and logged on successfully to the Virtual Centre server. All working ok again. I then changed the default DNS server on the Virtual Centre server to a physical DNS server to try to avoid a reoccurance.