Net APPS NAS access via Nortel Switching

we are working a issue where users are
experiencing very slow response copying
to/from a net apps box. When we try the
same identical process against a win2k
server the problem goes away. We have sniffed the traffic but there appears to
be no problem. We have been able to fix
the issue partly by turning Multi-link
trunking on between ethernet switches but by all the docs that we have reviewed this should not have to be done. Any IDEAS !!!!!!!! Thanks