file transfer reboots machine

In the office I work in, we use an accounting program on the workstation and export work done to the server so everyone can of course share in the knowledge that has been done.
Last week during file transfers to the server, about a third of the way into the transfer, the workstation reboots. I set up a "local" based program on the workstation and all the files tranferred fine. I tried it on the network again and the same thing, reboot. This leads me to believe it is a network problem but what I don't know. Any ideas? the workstations are win98 and the server in netware 4.11. Thanks
Brent