Peer to Peer Network problem

I have three computers that have been connected by way of windows 98 networking peer to peer system. For some reason they stopped holding a connection to each other. They see each other and I can view files on each of the other computers but when I try to create a map to a specific harddrive on another computer It seems to work but if I turn computer off the Mapped drive is gone. I have added computers to this network before and didn’t seem to have a problem then all of a sudden after upgrading one fo the computers to a PIII 700 I can’t seem to keep a link……