I'm trying to upgrade my ESXi host from 4.0 to 4.1. The host is currently running version 4.0.0, 332073. The host is running off an internal USB stick. I have tried the vihostupdate and receive the same error message as when I try via vSphere Client Update Manager tab. I have attached the log file from vSphere Update Manager. Originally I setup a 4.0 vCenter server and couldn't even get the update ZIP file to import. I then tried vCenter 4.1 and I got the update ZIP file to import, created a baseline for the upgrade, then tried the scan which failed with status "VMware vCenter Update Manager had an unknown error. Check the Tasks and Events tab and log files for details.".