I had a similar problem when I was using NT4 server and win98. If I remember correcty simply disable the master browser in win98 and XP this will stop the problem, and you can still browse at your leisure. I'm assuming your using samba as your default server?
Using the unc command as you've mentioned throu DOS works. If you dont see the win98/XP network neighbourhood icon simply use the dos Net use command it works every time. have fun