Networking

hi !
I have a prob with my switch.The prob is such that ihave two domains of diff o/s one NT other Novell.Both of them when
connected to a switch cannot communicate
but when connected to a hub can communicate.But when nt connected to switch and Novell connected to hub and hub connected to switch both nt and novell can communicate.Same ports are used in all the actions.And same prob persists with dif ports.
pls give a solu to this prob