Strange password error

[Dag]

I'm running samba 2.2.1 on and Origin200 with Irix 6.5.13 and I'm getting 
some strange password errors with some of my users.  The client machine 
always manages to log onto the server without problem after a while it fails 
to read and write files to the mounted samba filesystem and the following 
will apear in the log:

[2002/01/10 11:22:39, 2] lib/access.c:(316)
  Allowed connection from  (192.168.1.170)
[2002/01/10 11:22:39, 2] smbd/password.c:(586)
  pass_check_smb failed - invalid password for user [anet]
[2002/01/10 11:22:39, 2] smbd/password.c:(586)
  pass_check_smb failed - invalid password for user [anet]
[2002/01/10 11:22:39, 2] smbd/password.c:(586)
  pass_check_smb failed - invalid password for user [anet]
[2002/01/10 11:22:39, 2] smbd/service.c:(318)
  Invalid username/password for project [anet]

The user does not get prompted for a password again and the original login 
attempt is always succesfull.  Also this seems to only happen on a couple of 
the client machines.  All clients run win2K (SP1 or 2).  Any ideas?

Dag