[Samba] Slow first save operation from WinXP

[samba user]

Hello,

The first time I save a file from a winXP client, (from Word or other 
programs)
this takes a long time (12 secs or more).
Subsequent saves don't have this problem.

If I don't use the share for a longer period,
then this stalling happens again.

This problem does not happen when I just open a file,
or when I use explorer to copy a file to the share.

I did a fresh install of Debian Lenny,
added Samba through apt, with default configuration for the home shares,
and I'm still having the same problem.
I could not find anything similar on the Internet.

Samba 3.2.5 on Debian Lenny (5.0.4, fully up to date).
Clients: WinXP Home and Professional, English, fully updated (May 2010).

Has anyone seen something similar,
or have any ideas what might be happening?

Thanks,

Filip