CIFS mount intermittently unavailable: cifs_mount failed w/return code = -5

[Robert S <robert.spam.me.senseless@gmail.com>]

I have a debian machine called "debian" and a windows XP machine
called "server".  I have a permanent mounted read-only share called
\\server\doc.  My /etc/fstab looks like this:

//server/doc    /opt/chroot/mnt/server  cifs
credentials=/root/.smbmount,username=medical,uid=medical,file_mode=0755,dir_mode=0755,noserverino
      0   0

This works well most of the time but at times I get a input/output
error when I try to access this share.  My syslog shows the following:

Aug 16 15:36:35 debian kernel: [1289131.676869] Status code returned
0xc00000d0 NT_STATUS_REQUEST_NOT_ACCEPTED
Aug 16 15:36:35 debian kernel: [1289131.676875]  CIFS VFS: Send error
in SessSetup = -5
Aug 16 15:36:35 debian kernel: [1289131.676899]  CIFS VFS: cifs_mount
failed w/return code = -5
Aug 16 15:36:46 debian kernel: [1289142.653770] Status code returned
0xc00000d0 NT_STATUS_REQUEST_NOT_ACCEPTED
Aug 16 15:36:46 debian kernel: [1289142.653775]  CIFS VFS: Send error
in SessSetup = -5
Aug 16 15:36:46 debian kernel: [1289142.653799]  CIFS VFS: cifs_mount
failed w/return code = -5
Aug 16 15:37:01 debian kernel: [1289158.491697] Status code returned
0xc00000d0 NT_STATUS_REQUEST_NOT_ACCEPTED
Aug 16 15:37:01 debian kernel: [1289158.491703]  CIFS VFS: Send error
in SessSetup = -5
Aug 16 15:37:01 debian kernel: [1289158.491727]  CIFS VFS: cifs_mount
failed w/return code = -5

Does anyone have any suggestions?

I have tried replacing "server" with its fixed IP address
(192.168.0.32), but this does not help.  I have even moved all the
files to another location on the Windows box and recreated the share,
but it still occurs.