I don't know what the original poster did to fix his system, but from his esxupdate log the following message stands out:
2012-04-12T09:31:32Z esxupdate: HostImage: INFO: Installer <class 'vmware.esximage.Installer.BootBankInstaller.BootBankInstaller'> was not initiated - reason: altbootbank is invalid: Error in loading boot.cfg from bootbank /bootbank: Error parsing bootbank boot.cfg file /bootbank/boot.cfg: [Errno 2] No such file or directory: '/bootbank/boot.cfg'
Background: The disk image of a ESXi system is stored in a "bootbank" partition (5). When an update/patch is applied to the system, it does not change the bootbank. Instead it copies the bootbank to the alternate bootbank (altbootbank) partition (6) and applies the updates there. When the system is rebooted, the system detects that a update has occurred and swithches (kind of renames) the altbootbank(6) to bootbank and loads the system from the update image. So, after the system is rebooted, the bootbank is partition (6) and altbootbank is partition (5).
The error message indicates that the altbootbank invalid. I don't know why you would get that, but here are a few guesses:
1) As someone suggested, if you are using "autodeploy", then your system is 'diskless' (aka network boot) and there is no bootbank or altbootbank to use.
2) There was a hardware/software failure and somehow the disk/flash drive with the bootbank/altbootbank got disconnected from your system.
3) The altbootbank partition got corrupted.
For (1), you have to update the network boot image instead of your running image.
Trivia Note: in the case of (2), it is possible for the bootbank disk/flash to be removed from a running ESXi system without runtime errors. The bootbank is needed at boot time to load the system into a RAM disk, but it is not strictly needed after the system boots. One thing that will happen without the bootbank disk present on a running system is that configuration changes will get lost without someplace to store them between reboots.