Try removing the card from the winNT networking and re-installing. Also, use 98 to go and get the latest drivers from 3com, and then create some directories on your harddrive that both OS's can access, and put the driver files there, one directory per disk, (should be two disks for 3com drivers), then reinstall using a "have disk" and locate them.
For ease, make something like c:\3com\disk1,
c:\3com\disk2 to make your typeing easier.

If that doesn't work, then repost a reply.
l8r