You can resolve this issue by removing previously imported host upgrade release files and upgrading to Update Manager 4.1 Update 1 or later.
- If you imported any ESX/ESXi 4.1 or ESX/ESXi 4.1 Update 1 host upgrade releases in Update Manager 4.1, delete the host upgrade release files.
- If a host upgrade release is included in a baseline, in the Update Manager Baselines and Groups tab, edit or delete the baseline.
You cannot delete a host upgrade release that is included in a baseline.
- In the Host Upgrade Releases tab, delete the host upgrade release file.
- Upgrade vCenter Server and the vSphere Client to 4.1 Update 1.
You can use Update Manager only with a vCenter Server instance of the same version. For more information about upgrading vCenter Server, see the vSphere Upgrade Guide.
- Upgrade the Update Manager server and client plug-in to 4.1 Update 1.
For more information about upgrading Update Manager, see the VMware vCenter Update Manager Installation and Administration Guide (Chapter 7, Upgrading Update Manager).
- Import the necessary host upgrade releases in the Update Manager repository.
You import host upgrade releases from the Host Upgrade Releases tab in the Update Manager Administration view. The host upgrade release files differ depending on the source and target ESX/ESXi versions. For more information about baselines and host upgrade releases, see the VMware vCenter Update Manager Installation and Administration Guide(Chapter 12, Working with Baselines and Baseline Groups).
For a list of host upgrade release files, see VMware ESX 4.1 Update 1 Release Notes and VMware ESXi 4.1 Update 1 Release Notes.
- Create a host upgrade baseline that contains the necessary host upgrade release files.
You create baselines from the Baselines and Groups tab in the Update Manager Administration view.
- Remediate the hosts against the host upgrade baseline.
Based on VMware KB 1036035