I have upgraded 3 servers from 3.02 to 3.5 update 3. They are Dell PowerEdge 1955 blades. The upgrades were sucessful and the server rebooted fine after the upgrades. Afterwords, I scanned them with Update Manager and had it apply the 6 latest patches. Update manager then attempted to rebooted the server. The first server seemed to hang going down and I reset it. I rebooted it several times without any issues. The 2nd server I left and when I returned it had a PSOD. I rebooted it several times and it too seemed fine. I had the same thing happen to a 3rd and now see a pattern.
The error is "Lost Heartbeat". Fortunately, after sevel years of working with ESX this is the first PSOD's I have had. The servers have the latest bios, f/w, etc. Any thoughts?
PSOD's in most cases represent a hardware failure somewhere. If you can get the ESX on-line there should be a dump file in /root. If not, I found the best thing to do is a reinstall of the server. You may want to run some hardware diagnostics on it. But for me, sometimes a rebuild is better than diagnosing the problem.
Hope this helps!