What type of NAS and what type of connections are being used? 1 gig, 10 gig? Built in iSCSI adapter or something else?
Also, are these built in NIC ports or PCIe added nic ports? HP's are very touchy about having all the newest drivers, firmware and such installed before things like to work.
Built in or not, do they show up as nic cards under the Network Adapters view in the configuration tab?