vSphere 5.5 upgrade fails

I upgraded an ESXi host from 5.1 to 5.5u2 using the command line and downloading the image from vmware's deployment site.  It completes the update fine, but when I reboot, it gets to the point where the screen reads:  vfat loaded and then hangs until I hard reset. It reverts to the previous image and boots back to 5.1.

I have checked the logs in /var/log and there is nothing that I can find to explain this.

Any suggestions on where else to look for some clues as to why it failed to boot so I can troubleshoot?
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Is it possible that the 5.1 was installed from a vendor-customized version? There might be driver or other misconfigurations if you install a non-customized update edition over it.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Try using the ISO method of upgrading, what did you use on the command line ?

also make sure you are using the correct Offline file for this update, I've seen this issue, when users use the wrong update file. e.g. it's the incorrect file, and will not perform the update as intended.

e.g. use the offline depot file.

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michaelkim1Author Commented:
This solved the problem.  I was using the wrong update file.  Thank you.
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