Security info is not sent by the inventory scanner, it is sent using Vulscan.exe. Are all clients on the same agent version and configuration? Are they configured to scan at all?
Can you manually run a vulnerability scan on a system that does not show data and see what happens?
There are many reasons why this may not send but the best point to start at is by making sure they all use the same configuration and agent version; after that you can begin to see if you have a more serious problem.
Mark Star - MarXtar LANDesk Enhancements
Home of Power State Notifier & Wake-On-WAN for LANDesk