VMware has released a warning that upgrading from ESX 4.0 to 4.0 Update 1 on HP Proliant systems that run the HP Insight Management Agents can fail or time out and leave the host in an unusable state.

The full text of the relevant VMware KB article can be accessed <a href="http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&amp;cmd=displayKC&amp;externalId=1016070">here</a>.