Problems upgrading #VMWare ESX 4.0 to 4.0 Update 1

This is a bit scary

Source: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1016070

When attempting to upgrade ESX 4.0 to ESX 4.0 Update 1 (U1), you may experience these symptoms:

• Upgrade operation may fail or hang and can result in an incomplete installation
• Upon reboot, the host that was being upgraded may be left in an inconsistent state and may display a purple diagnostic screen with the following error:
  COS Panic: Int3 @ mp_register_ioapic

Who is affected

1. Customers using VMware vSphere 4 upgrading to ESX 4.0 U1 on HP Proliant systems with a supported version of HP Insight Management Agents running.
2. Customers running rpm commands on systems from any vendor while upgrading to ESX 4.0 U1.