Issue
If you try to scan a one/few ESXi 5.0 Hosts with "Scan for missing bulletins" you may get the following error:
Failed to load catalog for embeddedEsx.5.0.0, host ST.Virtual.Vim.HostSystem.
Reason
The reason behind this error message is that your ESXi server is not Internet facing, hence it cannot download the Metadata required to perform a scan or a patch deployment to the hypervisor's hosts.
Reminder : Pre-requisites to scan an Hypersvisor
All the prerequisites are listed in the following document :
http://community.shavlik.com/docs/DOC-22971
More information on how Protect scans and patches a hypervisor can be found in the following documents :