Are you installing the software first? Usually with Win98 you have to install the software/driver first, then plug in the hardware.
Also, when I install my Brother USB printer drivers, it asks me how the printer is connected-- local, local USB, network, or something else. In my haste I'm always tempted to hit "local," but just in the nick of time I see the "local USB" option. Maybe your drivers aren't set up right?