I am looking to see if anyone else has seen this issue. If a VM Guest was moved from one ESX Host to another by a VMotion or some other migration method, a new Network Discovery task of the VCenter will see the VM no longer resides on the Host it was originally found on and will delete the VM computer resource out of the NS. Eventually the Altiris agent on the VM guest will check into the NS and create a new computer resource. My issue is the Network Discovery task should not delete a computer resource out of the NS. I would expect it to remove the association it had with the VM guest and the Host, and assign the VM Guest to the new Host it now resides on.
I can see this action in the NS Logs by performing a migration in the VCenter of a VM Guest to another ESX Host. Run the Network Discovery task. The logs will show the VM Guest no longer can be found on the original Host and will delete the computer resource out of the NS. Later the Altiris agent will checkin to the NS and the computer reosurce is created, void of any CMDB/Asset data that may have been entered into the record.