Upgrade ESXi 4.1 to 5.x fails with error Downloading metadata failed.

I am trying to upgrade an ESXi 4.1 host to version 5.1 or 5.5. I tried updating it with PowerCLI and esxupdate. Below are the errors I am getting.

ESXUPDATE:
 esxupdate --bundle /vmfs/volumes/datastore1/ESXi-5.5.0-1331820-standard.zip update
error: Failed acquiring information for 'metadata-1284675570':
error: file:///var/tmp/cache/metadata-1284675570/ESXi/Packages.gz: File not found for validation
Encountered error MetadataFormatError:
The error data is:
   Filename    - None
   Message     - Failed scanning package data: Downloading metadata failed.
   Errno       - 5
   Description - The format of the metadata is invalid.



POWERCLI:
PowerCLI C:\> Get-VMHost | Install-VMHostPatch -HostPath /vmfs/volumes/datastore1/VMware-ESXi-5.1.0-799733-depot/vmw-ESXi-5.1.0-metadata.zip
Install-VMHostPatch : 9/26/2013 2:14:30 PM    Install-VMHostPatch        The following error occured while updating host '10.2.2.121': Failed scannin
g package data: Downloading metadata failed.
At line:1 char:33
+ Get-VMHost | Install-VMHostPatch <<<<  -HostPath /vmfs/volumes/datastore1/VMware-ESXi-5.1.0-799733-depot/vmw-ESXi-5.1.0-metadata.zip
    + CategoryInfo          : InvalidArgument: (:) [Install-VMHostPatch], VimException
    + FullyQualifiedErrorId : Client20_SystemManagementServiceImpl_InstallVMHostPatch40_InstallError,VMware.VimAutomation.ViCore.Cmdlets.Commands.Host.InstallVMHostPatch

Why is this failing? Am I doing something wrong?