Error encountered: An unknown error occurred while accessing the upgrade file

If you get an error ( Error encountered: An unknown error occurred while accessing the upgrade file ) while upgrading you might want to check the install log file for "ntp" and see if you have this error in the log. You must have an external NTP server before the upgrade will complete. * Note* this upgrade was on a vmare,CUCM 7.x to 8.x upgrade.
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VMware primary node MUST have external NTP server(s)|
08/03/2011 15:14:08 upgrade_os.sh|System info not updated by InstallWizard on new partition (1)|
08/03/2011 15:14:08 upgrade_manager.sh|Platform upgrade failed|

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CUCM 7.x NTP server won't sync

No matter what external NTP server I setup it wouldn't sync since the stratum was 16 on all of them. Not sure what was blocking this but once I changed the NTP server to the 2811 voice interface it synced properly. So if you do this make sure the 2811 has the correct time.