samba - Oct 1998 - session terminated

I have the 1.9.18p8  version  on a unix machine HP-UX 10.20
I try to connect from a pc with NT4.0 SP3 where I'm logged in as
"tec110"
On the samba server i have shared the fs /cadra/AB as [AB] and /cadra/AC as
[AC]
The  user  is able to cget the service from the pc with a tec110 and a pswd
but when i try to connect to the second service [AC] i have this msg :
"A  specified  logon  session  does  not  exist.  It  may already have been
terminated"
If  I  disconnect  the first connection [AB] I'm able to connect the second
[AC].Not at the same time.
Only one service is permitted ?

This is the "smb.conf" file :

[global]
  debug level = 2
# dead time = 5
# dns proxy = no
# security = USER
# browseable = yes
  encrypt passwords = yes
# max log size = 1000
  workgroup = SISINFO1
  password level = 8
# netbios name = cadtest
# interfaces = 10.1.5.1/255.255.0.0 10.101.5.1/255.255.0.0
  status = yes
  log file = /usr/local/samba/var/log.%m
  share modes = yes
#
#
[AB]
  comment = prova di condivisione con pc
  path = /cadra/AB
#
  allow hosts = gd01097, pag7c9, cadnt4, pag5e9, ast_port
  valid users = cadcam,  tec072,     gd, tec410,    lollo, tec110
  browseable = yes
  create mode = 0770
# preexec = csh -c 'echo "collegamento effettuato a %P di %h" |
/usr/local/samba/bin/smbclient -M %m -I %I'
  printable = no
  public = no
  veto files /cadra_db/*matrix*/*lost+found*/*storici*/*cadra_pro*/*stor*/
  writable = yes
#
[AC]
  comment = prova di condivisione con pc
  path = /cadra/AC
#
  allow hosts = gd01097, pag7c9, cadnt4, pag5e9, ast_port
  valid users = cadcam,  tec072,     gd, tec410,    lollo, tec110
  browseable = yes
  create mode = 0770
# preexec = csh -c 'echo "collegamento effettuato a %P di %h" |
/usr/local/samba/bin/smbclient -M %m -I %I'
  printable = no
  public = yes
  veto files /cadra_db/*matrix*/*lost+found*/*storici*/*cadra_pro*/*stor*/
  writable = no

active daemon on the unix machine
/usr/local/samba/bin/smbd -D
/usr/local/samba/bin/nmbd -D

Thank you