samba - Oct 2005 - Samba 3.0 serving DOS clients

I just upgrade from Samba 2.2.7a on RH9 to Samba
3.0.14a on FC4, all other clients are happy but the
DOS ones: they cannot launch the .bat files. From
sniffer capture, it seems that the server return a
filename in lower case which is unacceptable to DOS
client.

I tried to mangle with 'unix charset' and 'dos
charset' in smb.conf but cannot fix it. I really don't
want to fall back.......