Selective Inventory

I'm running ZFD4.0.1 on a NetWare 6.0 box. I'm trying to do inventory.
Many of the workstations will have an inventory done and the information
will show up in C1. Many workstations won't have an inventory done. I
have Windows XP workstations throughout, all on SP2, none have the
firewall running. All have the latest version of the management agent
running, all have the same client. There are no errors on the server.

Any ideas where I can start looking?