Do *any* of your computers work?
Another thing to be sure of is that your computer is processing Inventory scans.
Check the \ManagementSuite\LDScan folder to see if there are scan files stacked up in there. You may need to restart the LANDesk Inventory service.
The server needs to be able to process the miniscans that get sent in from clients that contain the MAC Address and other information.
It is also possible that the network card drivers are not entirely correct.
What model is the computer in question?