Upgrading ESX 4.0 to Update 1 using Update Manager when there are 3rd party management agents in the Console will result in an UNRECOVERABLE system.
Here is the official word from the KB as of now (11/25/2009 : 5 pm EST)
Upgrading ESX 4.0 to 4.0 U1 using Update Manager fails or times out and rebooting host results in a purple diagnostic screen
When attempting to upgrade ESX 4.0 to ESX 4.0 Update 1, you may experience the following symptoms:
- Update Manager (VUM) upgrade operation fails or times out at 33%.
- Upon reboot, the host that was being upgraded displays a purple diagnostic screen with the following error:
COS Panic: Int3 @ mp_register_ioapic
Who is affected
Customers using VMware vSphere 4 upgrading to Update 1 with 3rd party management agents running.
To avoid this issue, prior to the update, disable all 3rd party management agents running on the ESX 4.0.0 server before applying the update.
Note: The 3rd party management agents can be enabled after the upgrade is completed.
The official KB is here : http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1016070 and is being updated as information is released; I would imagine a patch link will appear there when it is ready.