I'm having somewhat the same problem.
I picked up a Linksys 5 port switch to use with my @Home ISP with a Motorola SB4100 modem. Both PC's are running Win98 SE and are able to acces the internet. However, no matter how hard I try, or which combination of networking protocols I try, the computers do not see eachother on the Network Neighbourhood.
If I connect the computers directly with a X-over cable, everything's fine. But it doesn't seem to work with the switch. Linksys assured me that this should work, but I can't figure it out for the life of me!
Could anyone help?