Is your vCenter in a VM? I'd say this was network / responsiveness related to your setup. I have the client on many support machines, never seen this problem.
the client has other refresh issues for VM's but they are minor, but not with the console of a VM.
600 seconds is short? What are you using an hour glass? 600 seconds is timeout, meaning the client WAITS for something to happen then when the timer is reached it will "timeout"