samba - Feb 2001 - weird

I have a samba file server in a network on school.(mandrake 7.2)
I use it as server for vcd files (virual cd). I have a share /data that
is public
I'm only able to connect from let's say 3 computers. Sometimes more. Is
it a hardware problem? how do I solve that (now 3com 3c509). I tried
also other (NE, AMDPCNET,...)
Sometimes the win98boxes don't find the server in their network
neigbourhood.
What should I try.
When I use my laptop as samba server (same config) I dont have the
problem.

Thanks