samba - Jul 2005 - receive_smb: SMB Signature verification failed on incoming packet

Hello,

I am trying to connect a 2nd Linux machine to my Samba PDC using 
smbmount. Both machines run Samba 3.0.14a. However, when trying to mount 
using

machine2# /usr/local/samba/bin/smbmount //pdc/wpkg /raid/samba/mount -o 
username=abc,password=123

it takes some seconds and then only brings up an I/O error. The log on 
the primary machine brings up

[2005/07/19 10:28:36, 1, effective(1008, 1008), real(1008, 0)] 
smbd/service.c:make_connection_snum(642)
   192.168.x.y (192.168.x.y) signed connect to service share initially 
as user user (uid=1008, gid=1008) (pid 10480)
[2005/07/19 10:28:36, 0, effective(0, 0), real(0, 0)] 
libsmb/smb_signing.c:srv_check_incoming_message(779)
   srv_check_incoming_message: BAD SIG: seq 4 wanted SMB signature of
[2005/07/19 10:28:36, 0, effective(0, 0), real(0, 0)] 
libsmb/smb_signing.c:srv_check_incoming_message(783)
   srv_check_incoming_message: BAD SIG: seq 4 got SMB signature of
[2005/07/19 10:28:36, 0, effective(0, 0), real(0, 0)] 
libsmb/smb_signing.c:signing_good(240)
   signing_good: BAD SIG: seq 4
[2005/07/19 10:28:36, 0, effective(0, 0), real(0, 0)] 
lib/util_sock.c:receive_smb(619)
   receive_smb: SMB Signature verification failed on incoming packet!
[2005/07/19 10:28:36, 1, effective(0, 0), real(0, 0)] 
smbd/service.c:close_cnum(830)
   192.168.x.y (192.168.x.y) closed connection to service share

Anyone knows what this is? Disabling server signing helps, but I guess 
this is not a good security setting...

Thanks
Florian