[Samba] slow directory browsing w2k and win xp

[mh]

hi everybody!

i´ve got a little problem with my samba 3.0.10-2.

when i connect from any w2k or win xp client in 
the lan area to my linux smb server there is no problem
but if i mount shares and go to some directory and 
select a file bigger than 3 KB the client machine freezes.
(directories or file smaller than 3 KB there is no problem;
also with win98 machines (all file sizes))

any idea?

all the best
~mh