Network Adapters disappear in W2K server

A few times, on different W2K servers, I’ve seen the network adapters disappear from the control panel. Device manager shows them, and IPCONFIG shows them, but I can’t administer them properly. A reboot will fix it, but I can’t always reboot a production server. They are Dell 6400’s with Intel NICs, W2K SP3. Has anyone seen this?