I decided to take the plunge and remediate one of my ESX3.5 Hosts to U3. Everything seemed ok for several hours, then all of a sudden virtual machines on the remediated box (and only on that box) started resetting one after the other.
Virtual Machine Monitoring was turned on, with monitoring sensitivity set to the default medium level. I quickly turned off monitoring, which stopped the cascading reset.
Has anyone else experienced this issue? There was no isolation response, (otherwise all the VMs would have been reset). This never happened on U2.
All VM's experienced a forced reset after VMotion so tested it by shutting down a VM, moving it from the U2 to U3 host, and restarting. Same result, forced reset.
Also found the following in the system log of each vm:
Event ID: 44
Windows has detected that the system firmware (BIOS) was updated
previous firmware date = 01/30/08, current firmware date 07/22/08