All backup tasks fail after upgrade to ESX 4.1 with the following error message: VM lock failed. (Failed to acquire vm lock/vmfs/volumes/<Datastore UUID>/<vm name>/.vzmutex due to an SSH connection issue.)
This error occurs when vRanger is attempting to authenticate to a vSphere 4.1 ESX host using a non-root account that existed on the host prior to the upgrade.
Using the vSphere Client log directly into the affected host and select the Local Users & Groups tab.
Right click on the account and select Edit.
Under Shell Access verify that the “Grant shell access to this user” tab is checked. Click OK to save the change.
Next click on Permissions Tab, right click to add permission, select the user from the list, then assign administrator role from the drop down.
Now you should be able to login with this user from a Command line or from the GUI.
Please note that only vRanger version 4.5.3 and later are fully compatible with vSphere 4.1 ESX hosts.