no harm to try find out, but if it is a network problem I think it will also tell the same story on the wintel boxes which could be using the same network.
And if I was the comms guy that's what I will generally say in defence if a unix guy approached me and told me he suspected it's a network problem, I would say "the wintel guys don't have this problem, how come only you guys have it"
most likely the wintel boxes are themselves tuned and have their tcp RWIN values set higher than the unix boxes hence performing a lot better.